Water Changes (Numerical Analysis of Frequency & Amount)

  • We are currently upgrading MFK. thanks! -neo
K

KeithDenny

Gambusia
MFK Member
Feb 12, 2014
9
1
18
Johns Creek, GA
Water Changes (Numerical Analysis of Frequency & Amount)
All, I have often wondered about the wisdom of 20% weekly water changes to reduce nitrates and fish secretions that stunt their growth if not removed. It seemed insufficient in my mind. As a Finance guy, I decided to do the analysis assuming a base case of 100 nitrate inputs/waste added per week over a sample 20 week period – the results are the same if you go longer. The below analysis shows that frequent large water changes are the best (obvious), but infrequent large water changes are far superior to weekly small water changes. Note, I will make the comments below under the assumption that you are keeping fish that are not sensitive to large water changes.
First, the analysis shows that with small frequent water changes, the waste will continue to build until it reaches a stable but high level – this is true no matter how small or infrequent the changes, but the stable level will be high – too high in my mind. A 20% weekly change will result in a range of 4 to 5 times the weekly inputs. A 40% weekly change will result in a range of 1.5 to 2.5 times weekly inputs – twice as good right before a water change and almost three times as good just after a water change. An 80% weekly water change will result in a range of only 0.25 to 1.25 times weekly inputs. This is 4 times the amount removed as a weekly water change – but the results are significantly more than 4 times as good for all but the time just before the water change. Fish health is not measured by the quality of water right after the water change, but by the average during the week. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 516"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 40% changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 80% changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
40%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 73, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 65, bgcolor: transparent"]Removed
[/TD]
[TD="width: 73, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20​
[/TD]
[TD="width: 74, bgcolor: transparent"]
80​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
40​
[/TD]
[TD="width: 74, bgcolor: transparent"]
60​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
100​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80​
[/TD]
[TD="width: 73, bgcolor: transparent"]
20​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 55, bgcolor: transparent"]
180​
[/TD]
[TD="width: 66, bgcolor: transparent"]
36​
[/TD]
[TD="width: 74, bgcolor: transparent"]
144​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
160​
[/TD]
[TD="width: 66, bgcolor: transparent"]
64​
[/TD]
[TD="width: 74, bgcolor: transparent"]
96​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
120​
[/TD]
[TD="width: 65, bgcolor: transparent"]
96​
[/TD]
[TD="width: 73, bgcolor: transparent"]
24​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 55, bgcolor: transparent"]
244​
[/TD]
[TD="width: 66, bgcolor: transparent"]
49​
[/TD]
[TD="width: 74, bgcolor: transparent"]
195​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
196​
[/TD]
[TD="width: 66, bgcolor: transparent"]
78​
[/TD]
[TD="width: 74, bgcolor: transparent"]
118​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
124​
[/TD]
[TD="width: 65, bgcolor: transparent"]
99​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 55, bgcolor: transparent"]
295​
[/TD]
[TD="width: 66, bgcolor: transparent"]
59​
[/TD]
[TD="width: 74, bgcolor: transparent"]
236​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
218​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
131​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 55, bgcolor: transparent"]
336​
[/TD]
[TD="width: 66, bgcolor: transparent"]
67​
[/TD]
[TD="width: 74, bgcolor: transparent"]
269​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
231​
[/TD]
[TD="width: 66, bgcolor: transparent"]
92​
[/TD]
[TD="width: 74, bgcolor: transparent"]
138​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 55, bgcolor: transparent"]
369​
[/TD]
[TD="width: 66, bgcolor: transparent"]
74​
[/TD]
[TD="width: 74, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
238​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
143​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 55, bgcolor: transparent"]
395​
[/TD]
[TD="width: 66, bgcolor: transparent"]
79​
[/TD]
[TD="width: 74, bgcolor: transparent"]
316​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
243​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
146​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 55, bgcolor: transparent"]
416​
[/TD]
[TD="width: 66, bgcolor: transparent"]
83​
[/TD]
[TD="width: 74, bgcolor: transparent"]
333​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
246​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
147​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 55, bgcolor: transparent"]
433​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
346​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
247​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
148​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 55, bgcolor: transparent"]
446​
[/TD]
[TD="width: 66, bgcolor: transparent"]
89​
[/TD]
[TD="width: 74, bgcolor: transparent"]
357​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
248​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
149​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 55, bgcolor: transparent"]
457​
[/TD]
[TD="width: 66, bgcolor: transparent"]
91​
[/TD]
[TD="width: 74, bgcolor: transparent"]
366​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
249​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
149​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 55, bgcolor: transparent"]
466​
[/TD]
[TD="width: 66, bgcolor: transparent"]
93​
[/TD]
[TD="width: 74, bgcolor: transparent"]
373​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
249​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 55, bgcolor: transparent"]
473​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
378​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 55, bgcolor: transparent"]
478​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
382​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 55, bgcolor: transparent"]
482​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 55, bgcolor: transparent"]
486​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
389​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 55, bgcolor: transparent"]
489​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
391​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 55, bgcolor: transparent"]
491​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
393​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 55, bgcolor: transparent"]
493​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74"]
394​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 55"]
494​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[/TABLE]

Next, I took a look at what happens when you do changes every other week. 20% water changes results in a range of 7 to 9 times weekly inputs – way too high in my opinion! 40% water changes every other week result in a range of 3 to 5 times weekly inputs – even though this is the same amount of water removed as 20% weekly water changes, it is superior to 20% weekly water changes for the majority of the two week period and never gets worse. 80% water changes every two weeks results are 0.5 to 2.5 times weekly inputs – very low for most of the time and a manageable peak level. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 538"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 207, bgcolor: transparent, colspan: 3"]2x Per Month 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 192, bgcolor: transparent, colspan: 3"]2x Per Month 40% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 204, bgcolor: transparent, colspan: 3"]2x Per Month 80% Changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 68, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 76, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 65, bgcolor: transparent"]
40%​
[/TD]
[TD="width: 73, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
Weekly Waste​
[/TD]
[TD="width: 67, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 68, bgcolor: transparent"]Removed
[/TD]
[TD="width: 76, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 65, bgcolor: transparent"]Removed
[/TD]
[TD="width: 73, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 67, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
100​
[/TD]
[TD="width: 68, bgcolor: transparent"]
[/TD]
[TD="width: 76, bgcolor: transparent"]
100​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
100​
[/TD]
[TD="width: 65, bgcolor: transparent"]
[/TD]
[TD="width: 73, bgcolor: transparent"]
100​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
100​
[/TD]
[TD="width: 67, bgcolor: transparent"]
[/TD]
[TD="width: 74, bgcolor: transparent"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
200​
[/TD]
[TD="width: 68, bgcolor: transparent"]
40​
[/TD]
[TD="width: 76, bgcolor: transparent"]
160​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
200​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80​
[/TD]
[TD="width: 73, bgcolor: transparent"]
120​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"]
160​
[/TD]
[TD="width: 74, bgcolor: transparent"]
40​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
260​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
260​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
220​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
220​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
140​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
140​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
360​
[/TD]
[TD="width: 68, bgcolor: transparent"]
72​
[/TD]
[TD="width: 76, bgcolor: transparent"]
288​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
320​
[/TD]
[TD="width: 65, bgcolor: transparent"]
128​
[/TD]
[TD="width: 73, bgcolor: transparent"]
192​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
240​
[/TD]
[TD="width: 67, bgcolor: transparent"]
192​
[/TD]
[TD="width: 74, bgcolor: transparent"]
48​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
388​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
388​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
292​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
292​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
148​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
148​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
488​
[/TD]
[TD="width: 68, bgcolor: transparent"]
98​
[/TD]
[TD="width: 76, bgcolor: transparent"]
390​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
392​
[/TD]
[TD="width: 65, bgcolor: transparent"]
157​
[/TD]
[TD="width: 73, bgcolor: transparent"]
235​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
248​
[/TD]
[TD="width: 67, bgcolor: transparent"]
198​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
490​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
490​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
335​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
335​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
590​
[/TD]
[TD="width: 68, bgcolor: transparent"]
118​
[/TD]
[TD="width: 76, bgcolor: transparent"]
472​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
435​
[/TD]
[TD="width: 65, bgcolor: transparent"]
174​
[/TD]
[TD="width: 73, bgcolor: transparent"]
261​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
572​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
572​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
361​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
361​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
672​
[/TD]
[TD="width: 68, bgcolor: transparent"]
134​
[/TD]
[TD="width: 76, bgcolor: transparent"]
538​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
461​
[/TD]
[TD="width: 65, bgcolor: transparent"]
184​
[/TD]
[TD="width: 73, bgcolor: transparent"]
277​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
638​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
638​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
377​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
377​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
738​
[/TD]
[TD="width: 68, bgcolor: transparent"]
148​
[/TD]
[TD="width: 76, bgcolor: transparent"]
590​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
477​
[/TD]
[TD="width: 65, bgcolor: transparent"]
191​
[/TD]
[TD="width: 73, bgcolor: transparent"]
286​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
690​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
690​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
386​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
790​
[/TD]
[TD="width: 68, bgcolor: transparent"]
158​
[/TD]
[TD="width: 76, bgcolor: transparent"]
632​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
486​
[/TD]
[TD="width: 65, bgcolor: transparent"]
194​
[/TD]
[TD="width: 73, bgcolor: transparent"]
292​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
732​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
732​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
392​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
392​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
832​
[/TD]
[TD="width: 68, bgcolor: transparent"]
166​
[/TD]
[TD="width: 76, bgcolor: transparent"]
666​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
492​
[/TD]
[TD="width: 65, bgcolor: transparent"]
197​
[/TD]
[TD="width: 73, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
766​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
766​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
395​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
866​
[/TD]
[TD="width: 68, bgcolor: transparent"]
173​
[/TD]
[TD="width: 76"]
693​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
495​
[/TD]
[TD="width: 65, bgcolor: transparent"]
198​
[/TD]
[TD="width: 73"]
297​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
793​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76"]
793​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
397​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73"]
397​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63"]
893​
[/TD]
[TD="width: 68, bgcolor: transparent"]
179​
[/TD]
[TD="width: 76, bgcolor: transparent"]
714​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54"]
497​
[/TD]
[TD="width: 65, bgcolor: transparent"]
199​
[/TD]
[TD="width: 73, bgcolor: transparent"]
298​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[/TABLE]

Last, I took a look at monthly water changes of 80%. This results in a range of 1 to 5 times weekly inputs. I do not recommend this, but the data shows that it is still FAR superior to weekly water changes of 20% for the majority of the month and the peak period is still the same – even though you are taking the same amount of water out. So, for all but one day of the month your fish are swimming if much better quality water and the quality is effectively the same on the last day. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 369"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 204, bgcolor: transparent, colspan: 3"]1X Per Month 80% Changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 67, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 75, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 67, bgcolor: transparent"]Removed
[/TD]
[TD="width: 75, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20​
[/TD]
[TD="width: 74, bgcolor: transparent"]
80​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
100​
[/TD]
[TD="width: 67, bgcolor: transparent"]
[/TD]
[TD="width: 75, bgcolor: transparent"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 55, bgcolor: transparent"]
180​
[/TD]
[TD="width: 66, bgcolor: transparent"]
36​
[/TD]
[TD="width: 74, bgcolor: transparent"]
144​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
200​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 55, bgcolor: transparent"]
244​
[/TD]
[TD="width: 66, bgcolor: transparent"]
49​
[/TD]
[TD="width: 74, bgcolor: transparent"]
195​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
300​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
300​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 55, bgcolor: transparent"]
295​
[/TD]
[TD="width: 66, bgcolor: transparent"]
59​
[/TD]
[TD="width: 74, bgcolor: transparent"]
236​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
400​
[/TD]
[TD="width: 67, bgcolor: transparent"]
320​
[/TD]
[TD="width: 75, bgcolor: transparent"]
80​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 55, bgcolor: transparent"]
336​
[/TD]
[TD="width: 66, bgcolor: transparent"]
67​
[/TD]
[TD="width: 74, bgcolor: transparent"]
269​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
180​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
180​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 55, bgcolor: transparent"]
369​
[/TD]
[TD="width: 66, bgcolor: transparent"]
74​
[/TD]
[TD="width: 74, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
280​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
280​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 55, bgcolor: transparent"]
395​
[/TD]
[TD="width: 66, bgcolor: transparent"]
79​
[/TD]
[TD="width: 74, bgcolor: transparent"]
316​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
380​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
380​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 55, bgcolor: transparent"]
416​
[/TD]
[TD="width: 66, bgcolor: transparent"]
83​
[/TD]
[TD="width: 74, bgcolor: transparent"]
333​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
480​
[/TD]
[TD="width: 67, bgcolor: transparent"]
384​
[/TD]
[TD="width: 75, bgcolor: transparent"]
96​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 55, bgcolor: transparent"]
433​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
346​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
196​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
196​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 55, bgcolor: transparent"]
446​
[/TD]
[TD="width: 66, bgcolor: transparent"]
89​
[/TD]
[TD="width: 74, bgcolor: transparent"]
357​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
296​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
296​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 55, bgcolor: transparent"]
457​
[/TD]
[TD="width: 66, bgcolor: transparent"]
91​
[/TD]
[TD="width: 74, bgcolor: transparent"]
366​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
396​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
396​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 55, bgcolor: transparent"]
466​
[/TD]
[TD="width: 66, bgcolor: transparent"]
93​
[/TD]
[TD="width: 74, bgcolor: transparent"]
373​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
496​
[/TD]
[TD="width: 67, bgcolor: transparent"]
397​
[/TD]
[TD="width: 75, bgcolor: transparent"]
99​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 55, bgcolor: transparent"]
473​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
378​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
199​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
199​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 55, bgcolor: transparent"]
478​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
382​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
299​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
299​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 55, bgcolor: transparent"]
482​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
399​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
399​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 55, bgcolor: transparent"]
486​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
389​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
499​
[/TD]
[TD="width: 67, bgcolor: transparent"]
399​
[/TD]
[TD="width: 75"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 55, bgcolor: transparent"]
489​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
391​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
200​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 55, bgcolor: transparent"]
491​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
393​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
300​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
300​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 55, bgcolor: transparent"]
493​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74"]
394​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
400​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
400​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 55"]
494​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62"]
500​
[/TD]
[TD="width: 67, bgcolor: transparent"]
400​
[/TD]
[TD="width: 75, bgcolor: transparent"]
100​
[/TD]
[/TR]
[/TABLE]

Bottom line – small water changes are not sufficient, no matter how frequently they are performed. Large water changes are needed – preferable frequently, but infrequent large water changes are superior to multiple small water changes.
Let me know your thoughts – hopefully this helps,
Keith
 
Hopefully easier to read:

Water Changes (Numerical Analysis of Frequency & Amount)
All, I have often wondered about the wisdom of 20% weekly water changes to reduce nitrates and fish secretions that stunt their growth if not removed. It seemed insufficient in my mind. As a Finance guy, I decided to do the analysis assuming a base case of 100 nitrate inputs/waste added per week over a sample 20 week period – the results are the same if you go longer. The below analysis shows that frequent large water changes are the best (obvious), but infrequent large water changes are far superior to weekly small water changes. Note, I will make the comments below under the assumption that you are keeping fish that are not sensitive to large water changes.
First, the analysis shows that with small frequent water changes, the waste will continue to build until it reaches a stable but high level – this is true no matter how small or infrequent the changes, but the stable level will be high – too high in my mind. A 20% weekly change will result in a range of 4 to 5 times the weekly inputs. A 40% weekly change will result in a range of 1.5 to 2.5 times weekly inputs – twice as good right before a water change and almost three times as good just after a water change. An 80% weekly water change will result in a range of only 0.25 to 1.25 times weekly inputs. This is 4 times the amount removed as a weekly water change – but the results are significantly more than 4 times as good for all but the time just before the water change. Fish health is not measured by the quality of water right after the water change, but by the average during the week. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 516"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 40% changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 80% changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
40%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 73, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 65, bgcolor: transparent"]Removed
[/TD]
[TD="width: 73, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20​
[/TD]
[TD="width: 74, bgcolor: transparent"]
80​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
40​
[/TD]
[TD="width: 74, bgcolor: transparent"]
60​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
100​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80​
[/TD]
[TD="width: 73, bgcolor: transparent"]
20​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 55, bgcolor: transparent"]
180​
[/TD]
[TD="width: 66, bgcolor: transparent"]
36​
[/TD]
[TD="width: 74, bgcolor: transparent"]
144​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
160​
[/TD]
[TD="width: 66, bgcolor: transparent"]
64​
[/TD]
[TD="width: 74, bgcolor: transparent"]
96​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
120​
[/TD]
[TD="width: 65, bgcolor: transparent"]
96​
[/TD]
[TD="width: 73, bgcolor: transparent"]
24​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 55, bgcolor: transparent"]
244​
[/TD]
[TD="width: 66, bgcolor: transparent"]
49​
[/TD]
[TD="width: 74, bgcolor: transparent"]
195​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
196​
[/TD]
[TD="width: 66, bgcolor: transparent"]
78​
[/TD]
[TD="width: 74, bgcolor: transparent"]
118​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
124​
[/TD]
[TD="width: 65, bgcolor: transparent"]
99​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 55, bgcolor: transparent"]
295​
[/TD]
[TD="width: 66, bgcolor: transparent"]
59​
[/TD]
[TD="width: 74, bgcolor: transparent"]
236​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
218​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
131​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 55, bgcolor: transparent"]
336​
[/TD]
[TD="width: 66, bgcolor: transparent"]
67​
[/TD]
[TD="width: 74, bgcolor: transparent"]
269​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
231​
[/TD]
[TD="width: 66, bgcolor: transparent"]
92​
[/TD]
[TD="width: 74, bgcolor: transparent"]
138​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 55, bgcolor: transparent"]
369​
[/TD]
[TD="width: 66, bgcolor: transparent"]
74​
[/TD]
[TD="width: 74, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
238​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
143​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 55, bgcolor: transparent"]
395​
[/TD]
[TD="width: 66, bgcolor: transparent"]
79​
[/TD]
[TD="width: 74, bgcolor: transparent"]
316​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
243​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
146​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 55, bgcolor: transparent"]
416​
[/TD]
[TD="width: 66, bgcolor: transparent"]
83​
[/TD]
[TD="width: 74, bgcolor: transparent"]
333​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
246​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
147​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 55, bgcolor: transparent"]
433​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
346​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
247​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
148​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 55, bgcolor: transparent"]
446​
[/TD]
[TD="width: 66, bgcolor: transparent"]
89​
[/TD]
[TD="width: 74, bgcolor: transparent"]
357​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
248​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
149​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 55, bgcolor: transparent"]
457​
[/TD]
[TD="width: 66, bgcolor: transparent"]
91​
[/TD]
[TD="width: 74, bgcolor: transparent"]
366​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
249​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
149​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 55, bgcolor: transparent"]
466​
[/TD]
[TD="width: 66, bgcolor: transparent"]
93​
[/TD]
[TD="width: 74, bgcolor: transparent"]
373​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
249​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 55, bgcolor: transparent"]
473​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
378​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 55, bgcolor: transparent"]
478​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
382​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 55, bgcolor: transparent"]
482​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 55, bgcolor: transparent"]
486​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
389​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 55, bgcolor: transparent"]
489​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
391​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 55, bgcolor: transparent"]
491​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
393​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 55, bgcolor: transparent"]
493​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74"]
394​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57, bgcolor: transparent"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73"]
25​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 55"]
494​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 55"]
250​
[/TD]
[TD="width: 66, bgcolor: transparent"]
100​
[/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 57"]
125​
[/TD]
[TD="width: 65, bgcolor: transparent"]
100​
[/TD]
[TD="width: 73, bgcolor: transparent"]
25​
[/TD]
[/TR]
[/TABLE]

Next, I took a look at what happens when you do changes every other week. 20% water changes results in a range of 7 to 9 times weekly inputs – way too high in my opinion! 40% water changes every other week result in a range of 3 to 5 times weekly inputs – even though this is the same amount of water removed as 20% weekly water changes, it is superior to 20% weekly water changes for the majority of the two week period and never gets worse. 80% water changes every two weeks results are 0.5 to 2.5 times weekly inputs – very low for most of the time and a manageable peak level. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 538"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 207, bgcolor: transparent, colspan: 3"]2x Per Month 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 192, bgcolor: transparent, colspan: 3"]2x Per Month 40% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 204, bgcolor: transparent, colspan: 3"]2x Per Month 80% Changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 68, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 76, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 65, bgcolor: transparent"]
40%​
[/TD]
[TD="width: 73, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
Weekly Waste​
[/TD]
[TD="width: 67, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 68, bgcolor: transparent"]Removed
[/TD]
[TD="width: 76, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 65, bgcolor: transparent"]Removed
[/TD]
[TD="width: 73, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 67, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
100​
[/TD]
[TD="width: 68, bgcolor: transparent"]
[/TD]
[TD="width: 76, bgcolor: transparent"]
100​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
100​
[/TD]
[TD="width: 65, bgcolor: transparent"]
[/TD]
[TD="width: 73, bgcolor: transparent"]
100​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
100​
[/TD]
[TD="width: 67, bgcolor: transparent"]
[/TD]
[TD="width: 74, bgcolor: transparent"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
200​
[/TD]
[TD="width: 68, bgcolor: transparent"]
40​
[/TD]
[TD="width: 76, bgcolor: transparent"]
160​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
200​
[/TD]
[TD="width: 65, bgcolor: transparent"]
80​
[/TD]
[TD="width: 73, bgcolor: transparent"]
120​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"]
160​
[/TD]
[TD="width: 74, bgcolor: transparent"]
40​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
260​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
260​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
220​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
220​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
140​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
140​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
360​
[/TD]
[TD="width: 68, bgcolor: transparent"]
72​
[/TD]
[TD="width: 76, bgcolor: transparent"]
288​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
320​
[/TD]
[TD="width: 65, bgcolor: transparent"]
128​
[/TD]
[TD="width: 73, bgcolor: transparent"]
192​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
240​
[/TD]
[TD="width: 67, bgcolor: transparent"]
192​
[/TD]
[TD="width: 74, bgcolor: transparent"]
48​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
388​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
388​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
292​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
292​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
148​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
148​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
488​
[/TD]
[TD="width: 68, bgcolor: transparent"]
98​
[/TD]
[TD="width: 76, bgcolor: transparent"]
390​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
392​
[/TD]
[TD="width: 65, bgcolor: transparent"]
157​
[/TD]
[TD="width: 73, bgcolor: transparent"]
235​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
248​
[/TD]
[TD="width: 67, bgcolor: transparent"]
198​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
490​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
490​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
335​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
335​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
590​
[/TD]
[TD="width: 68, bgcolor: transparent"]
118​
[/TD]
[TD="width: 76, bgcolor: transparent"]
472​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
435​
[/TD]
[TD="width: 65, bgcolor: transparent"]
174​
[/TD]
[TD="width: 73, bgcolor: transparent"]
261​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
572​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
572​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
361​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
361​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
672​
[/TD]
[TD="width: 68, bgcolor: transparent"]
134​
[/TD]
[TD="width: 76, bgcolor: transparent"]
538​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
461​
[/TD]
[TD="width: 65, bgcolor: transparent"]
184​
[/TD]
[TD="width: 73, bgcolor: transparent"]
277​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
638​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
638​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
377​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
377​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
738​
[/TD]
[TD="width: 68, bgcolor: transparent"]
148​
[/TD]
[TD="width: 76, bgcolor: transparent"]
590​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
477​
[/TD]
[TD="width: 65, bgcolor: transparent"]
191​
[/TD]
[TD="width: 73, bgcolor: transparent"]
286​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
690​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
690​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
386​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
790​
[/TD]
[TD="width: 68, bgcolor: transparent"]
158​
[/TD]
[TD="width: 76, bgcolor: transparent"]
632​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
486​
[/TD]
[TD="width: 65, bgcolor: transparent"]
194​
[/TD]
[TD="width: 73, bgcolor: transparent"]
292​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
732​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
732​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
392​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
392​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
832​
[/TD]
[TD="width: 68, bgcolor: transparent"]
166​
[/TD]
[TD="width: 76, bgcolor: transparent"]
666​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
492​
[/TD]
[TD="width: 65, bgcolor: transparent"]
197​
[/TD]
[TD="width: 73, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
766​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76, bgcolor: transparent"]
766​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
395​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74, bgcolor: transparent"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
866​
[/TD]
[TD="width: 68, bgcolor: transparent"]
173​
[/TD]
[TD="width: 76"]
693​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
495​
[/TD]
[TD="width: 65, bgcolor: transparent"]
198​
[/TD]
[TD="width: 73"]
297​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74"]
50​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
793​
[/TD]
[TD="width: 68, bgcolor: transparent"][/TD]
[TD="width: 76"]
793​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54, bgcolor: transparent"]
397​
[/TD]
[TD="width: 65, bgcolor: transparent"][/TD]
[TD="width: 73"]
397​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63, bgcolor: transparent"]
150​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 74"]
150​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63"]
893​
[/TD]
[TD="width: 68, bgcolor: transparent"]
179​
[/TD]
[TD="width: 76, bgcolor: transparent"]
714​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 54"]
497​
[/TD]
[TD="width: 65, bgcolor: transparent"]
199​
[/TD]
[TD="width: 73, bgcolor: transparent"]
298​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 63"]
250​
[/TD]
[TD="width: 67, bgcolor: transparent"]
200​
[/TD]
[TD="width: 74, bgcolor: transparent"]
50​
[/TD]
[/TR]
[/TABLE]

Last, I took a look at monthly water changes of 80%. This results in a range of 1 to 5 times weekly inputs. I do not recommend this, but the data shows that it is still FAR superior to weekly water changes of 20% for the majority of the month and the peak period is still the same – even though you are taking the same amount of water out. So, for all but one day of the month your fish are swimming if much better quality water and the quality is effectively the same on the last day. See below for weekly analysis:
[TABLE="class: MsoNormalTable, width: 369"]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 195, bgcolor: transparent, colspan: 3"]Weekly 20% Changes
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 204, bgcolor: transparent, colspan: 3"]1X Per Month 80% Changes
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 55, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20%​
[/TD]
[TD="width: 74, bgcolor: transparent"]
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
Ending Waste​
[/TD]
[TD="width: 67, bgcolor: transparent"]
80%​
[/TD]
[TD="width: 75, bgcolor: transparent"]
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"][/TD]
[TD="width: 66, bgcolor: transparent"]Removed
[/TD]
[TD="width: 74, bgcolor: transparent"]Remaining
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 67, bgcolor: transparent"]Removed
[/TD]
[TD="width: 75, bgcolor: transparent"]Remaining
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 1
[/TD]
[TD="width: 55, bgcolor: transparent"]
100​
[/TD]
[TD="width: 66, bgcolor: transparent"]
20​
[/TD]
[TD="width: 74, bgcolor: transparent"]
80​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
100​
[/TD]
[TD="width: 67, bgcolor: transparent"]
[/TD]
[TD="width: 75, bgcolor: transparent"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 2
[/TD]
[TD="width: 55, bgcolor: transparent"]
180​
[/TD]
[TD="width: 66, bgcolor: transparent"]
36​
[/TD]
[TD="width: 74, bgcolor: transparent"]
144​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
200​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 3
[/TD]
[TD="width: 55, bgcolor: transparent"]
244​
[/TD]
[TD="width: 66, bgcolor: transparent"]
49​
[/TD]
[TD="width: 74, bgcolor: transparent"]
195​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
300​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
300​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 4
[/TD]
[TD="width: 55, bgcolor: transparent"]
295​
[/TD]
[TD="width: 66, bgcolor: transparent"]
59​
[/TD]
[TD="width: 74, bgcolor: transparent"]
236​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
400​
[/TD]
[TD="width: 67, bgcolor: transparent"]
320​
[/TD]
[TD="width: 75, bgcolor: transparent"]
80​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 5
[/TD]
[TD="width: 55, bgcolor: transparent"]
336​
[/TD]
[TD="width: 66, bgcolor: transparent"]
67​
[/TD]
[TD="width: 74, bgcolor: transparent"]
269​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
180​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
180​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 6
[/TD]
[TD="width: 55, bgcolor: transparent"]
369​
[/TD]
[TD="width: 66, bgcolor: transparent"]
74​
[/TD]
[TD="width: 74, bgcolor: transparent"]
295​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
280​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
280​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 7
[/TD]
[TD="width: 55, bgcolor: transparent"]
395​
[/TD]
[TD="width: 66, bgcolor: transparent"]
79​
[/TD]
[TD="width: 74, bgcolor: transparent"]
316​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
380​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
380​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 8
[/TD]
[TD="width: 55, bgcolor: transparent"]
416​
[/TD]
[TD="width: 66, bgcolor: transparent"]
83​
[/TD]
[TD="width: 74, bgcolor: transparent"]
333​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
480​
[/TD]
[TD="width: 67, bgcolor: transparent"]
384​
[/TD]
[TD="width: 75, bgcolor: transparent"]
96​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 9
[/TD]
[TD="width: 55, bgcolor: transparent"]
433​
[/TD]
[TD="width: 66, bgcolor: transparent"]
87​
[/TD]
[TD="width: 74, bgcolor: transparent"]
346​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
196​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
196​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 10
[/TD]
[TD="width: 55, bgcolor: transparent"]
446​
[/TD]
[TD="width: 66, bgcolor: transparent"]
89​
[/TD]
[TD="width: 74, bgcolor: transparent"]
357​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
296​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
296​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 11
[/TD]
[TD="width: 55, bgcolor: transparent"]
457​
[/TD]
[TD="width: 66, bgcolor: transparent"]
91​
[/TD]
[TD="width: 74, bgcolor: transparent"]
366​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
396​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
396​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 12
[/TD]
[TD="width: 55, bgcolor: transparent"]
466​
[/TD]
[TD="width: 66, bgcolor: transparent"]
93​
[/TD]
[TD="width: 74, bgcolor: transparent"]
373​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
496​
[/TD]
[TD="width: 67, bgcolor: transparent"]
397​
[/TD]
[TD="width: 75, bgcolor: transparent"]
99​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 13
[/TD]
[TD="width: 55, bgcolor: transparent"]
473​
[/TD]
[TD="width: 66, bgcolor: transparent"]
95​
[/TD]
[TD="width: 74, bgcolor: transparent"]
378​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
199​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
199​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 14
[/TD]
[TD="width: 55, bgcolor: transparent"]
478​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
382​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
299​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
299​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 15
[/TD]
[TD="width: 55, bgcolor: transparent"]
482​
[/TD]
[TD="width: 66, bgcolor: transparent"]
96​
[/TD]
[TD="width: 74, bgcolor: transparent"]
386​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
399​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75, bgcolor: transparent"]
399​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 16
[/TD]
[TD="width: 55, bgcolor: transparent"]
486​
[/TD]
[TD="width: 66, bgcolor: transparent"]
97​
[/TD]
[TD="width: 74, bgcolor: transparent"]
389​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
499​
[/TD]
[TD="width: 67, bgcolor: transparent"]
399​
[/TD]
[TD="width: 75"]
100​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 17
[/TD]
[TD="width: 55, bgcolor: transparent"]
489​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
391​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
200​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
200​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 18
[/TD]
[TD="width: 55, bgcolor: transparent"]
491​
[/TD]
[TD="width: 66, bgcolor: transparent"]
98​
[/TD]
[TD="width: 74, bgcolor: transparent"]
393​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
300​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
300​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 19
[/TD]
[TD="width: 55, bgcolor: transparent"]
493​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74"]
394​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62, bgcolor: transparent"]
400​
[/TD]
[TD="width: 67, bgcolor: transparent"][/TD]
[TD="width: 75"]
400​
[/TD]
[/TR]
[TR]
[TD="width: 83, bgcolor: transparent"]Week 20
[/TD]
[TD="width: 55"]
494​
[/TD]
[TD="width: 66, bgcolor: transparent"]
99​
[/TD]
[TD="width: 74, bgcolor: transparent"]
395​
[/TD]
[TD="width: 11, bgcolor: transparent"][/TD]
[TD="width: 62"]
500​
[/TD]
[TD="width: 67, bgcolor: transparent"]
400​
[/TD]
[TD="width: 75, bgcolor: transparent"]
100​
[/TD]
[/TR]
[/TABLE]

Bottom line – small water changes are not sufficient, no matter how frequently they are performed. Large water changes are needed – preferable frequently, but infrequent large water changes are superior to multiple small water changes.
Let me know your thoughts – hopefully this helps,
Keith
 
You must log in or register to reply here.
MonsterFishKeepers.com
Top Bottom