an exhaustive explanation to Water Change Theory

[hardb0iled]

My theory on water changes is this:

I believe fish will acclimatise to certain water parameters, not to say that a certain level of nitrates wont bother the fish but they will become accustomed to certain temperature, PH, hardness etc that they are exposed to everyday in the aquarium.

Doing a large water change may be the most effective way to reduce nitrates, but it also throws all your other water parameters out instantly(tap water is never identical in composition to your tank water), so the fish suddenly find themselves in a stressful situation until they re-acclimatise to the water conditions or the water conditions are adjusted to what they previously were.

As is explained above, small more regular water changes probably is beneficial in this case at reducing the stress on the fish but not as effective at reducing accumulating Nitrate levels.

So basically what you need to do is be aware of all these effects and armed with this information, make your own mind up as to whats the best compromise (large infrequent vs small frequent) that best suits your fish

The best possible scenario would be to have a large reserve of water in a holding tank that is adjusted to the same parameters as the aquarium(minus the nitrates) and do large regular water changes from the holding tank, but of course this is just impractical for most aquarists!

 

[CentralMayhem]

go large and frequent. if you do that from the time the tank is cycled then you will never even have an accumulation of harmful substances. if you dont do REGULAR large scale water changes from the beginning and then all of the sudden do a 90% change on a dirty tank then YES you will more than likely encounter problems. but i think we are jacking shekes thread again, so ill stop now.

 

[Jesse]

I'm a fan of large (40-60%) regular water changes. Assuming that your tap water has zero nitrates, the percentage water change equals the percentage reduction in nitrates--it's a linear relationship.

Assuming that your aquarium nitrate concentration goes up by 10 ppm per week, you'll actually end up with a lower nitrate concentration at the end of the month by doing bi-weekly 50% water changes than you would doing weekly 25% water changes.

25% weekly water changes
end of week 1 = 10 ppm x .75 (25% water change) = 7.5 ppm after water change
end of week 2 = 17.5 ppm x .75 = 13.125 ppm after water change
end of week 3 = 23.125 ppm x .75 = 17.34 ppm after water change
end of week 4 = 27.34 ppm x .75 = 20.5 ppm

50% bi-weekly water changes
end of week 1 = 10 ppm (no water change)
end of week 2 = 20 ppm x .50 (50% water change) = 10 ppm after water change
end of week 3 = 20 ppm (no water change)
end of week 4 = 30 ppm x .50 = 15 ppm

You get even better results if you do the larger water changes more frequently.

 

[DeLgAdO]

 

[repair]

The best possible scenario would be to have a large reserve of water in a holding tank that is adjusted to the same parameters as the aquarium(minus the nitrates) and do large regular water changes from the holding tank, but of course this is just impractical for most aquarists!

Have you seen my post about the drip system?

 

[shekes]

I thought I revive this thread to replace JardiniBoy's badly worded article.

 

[Lil_Stinker]

.....
Remember changing the frequency and the amount in proportion will only change the variance not the normalization so changing 1/12th every hour will still be the same just a difference variance. you will fluctuate 1 hours waste over the normal line.

That should have been under .

Gosh !!
I would recommend a system that changes water at a constant rate. This will minimize the variance in the baseline caused by waste buildup between water changes, as well a the potential shock to the fish.

In a practical world, this can be done. But even with continuous water changes, assume a rate of 50% over 1 week, you will still end up being stable at a constant 2 weeks of waste in the tank.

As crazy as it sounds; no matter what frequency you change water, the rate will determine the solution.

70% a week or 10 % a day will result in the same MAX pollutants.
Frequency = daily vs weekly
Rate is the same 70% per week

70% weekly change will have max pollutants of about 1.428571 weeks worth.
..... My dang head is killing me....

Even if the change is done

Every 12 hours 5%
Every 6 hours 2.5 %
Every 3 hours 1.25%
Every 1 hour 0.4166666666%

Your max pollutants will still be 1.428571 weeks of polution in the tank.

No matter how often you change water you are still removing some of the clean water.

******

If you skip 6 weeks (pollutants skyrocket to 7.1428571 weeks worth) then start on the same routine again, you will still normalize at 1.428571 weeks pollutants.

The only thing the frequency of a waterchange does is reduces the variance off normal, therefore reducing stress.

If you change 70% per week you will max at 1.428571 weeks pollutants; after your change you will be at 0.428571 weeks polutants. (big change)

If you change 10% every day then you will max at 1.428571 weeks pollutants; after your change you will be at 1.285713593 weeks polutants. (smaller change, less stress)

If you change 5% every 12 hours then you will max at 1.428571 weeks pollutants; after your change you will be at 1.357142843 weeks polutants. (even smaller change, even less stress)

If you change 0.41666% every 1 hour then you will max at 1.428571 weeks pollutants; after your change you will be at 1.416661862 weeks polutants. (Super small change, Super less stress)

If you set a auto drip constant change to change 100% in a week, you will normalize and keep a constant 1 weeks pollutants in the tank.



All that being said I reference the origination of this thread

There are sooo many threads on WCs and I always encounter the same mistake:
People believe that 2 small WCs are the same as one big one as long as they change the same amount of water. It is wrong.
If you do 2 WCs, when doing the second one, part of the water you pump/suck/siphon out is the "clean" water you put in in the first waterchange......

....... Not thaaaaat complicated really.

Not only do I believe that two 25% changes in 1 week are the same as one 50% change per week, I have proven it.

Max polutants stay the same once normalized. The larger and less frequent the changes are, the more variance under the normal line & the more stress to the fish.

Change less, more often !!!

Yes I did quote myself .. & I can show you the math if it helps

 

[shekes]

Thank you for trying to help!

To preemt a misunderstanding: the sentence you are quoting is only valid if the second WC of 25% is performed at the same time or earlier as the 50% change would be. If you perform it later it may give differnt results.
I saw your previous posts but haven't read them because I don't enjoy calculating numbers and because they are not at all necessary. I also don't know what you mean by "variance" and "normalization". Generally the former expression stands for the square root of the sum of sqared deviations from the average. As to the second, I never even heard of it.
My fromula and conclusion are definitely correct. If you have any doubt I invite you to express it but I do ask you to abstain from numbers and be clear what it is you do not understand/dispute or disagee with. For now you just posted some numbers withou even explaining how it is you arrived at them. It isn't helpful like that.

I am happy explaining things to people. But, as you know I've already spent a day explaining the obvious and don't want to waste my time again.

 

[Lil_Stinker]

I sincerely apologize for any confusion. I hope that the following will clear things up. I understand that in print, it is easy to come off sounding arrogant, ignorant and/or rude. Please understand that I am merely attempting to show the point & the math and dictionary references are simply to support the display.

from m-w.com

Main Entry: nor·mal·ize
Pronunciation: 'nor-m&-"lIz
Function: transitive verb
Inflected Form(s): -ized; -iz·ing
1 : to make conform to or reduce to a norm or standard
2 : to make normal (as by a transformation of variables)
3 : to bring or restore (as relations between countries) to a normal condition


This is the presumed maximum waste saturation, which in the case of a continuous water change will be constant.

With regular water changes The levels of waste will continue to rise (or fall) until they reach a level that is "normal" to the rate of change.

Over time a continuous water change at 100% per week will 'normalize' the tank at a level of about 1-week’s waste.


Main Entry: var·i·ance
Pronunciation: 'ver-E-&n(t)s
Function: noun
1 : the fact, quality, or state of being variable or variant : DIFFERENCE, VARIATION <yearly variance in crops>
2 : the fact or state of being in disagreement : DISSENSION, DISPUTE
3 : a disagreement between two parts of the same legal proceeding that must be consonant
4 : a license to do some act contrary to the usual rule <a zoning variance>
5 : the square of the standard deviation

This is the change from the "norm" caused by the (in) frequency of the water change.

Change 10% at 16.8-hour intervals (10 times per week) will cause a variance from the norm. This variance will decrease with the increase in frequency (decrease in volume) of the changes.

In short; my point is if, at the end of the week, you have changed the same total amount of water, then you have minimized the shock to the fish by reducing the "change".

I do agree, however, that the average pollutants are lower with larger, less frequent water changes, as is the post water change level.

A continuous 100% per week change will be stable and average at or about the norm of 1 weeks waste.

If one were to change 100% each week then the "average" (on the day of the change) will be 1/2 weeks waste and the post change levels will be zero. Although the max is the same, and the average is lower, the variance is huge.

 

[HarleyK]

Guys,

This discussion of yours is going nowhere and it is not contributing anything beyond what has already been said. I think the point has been made that water changes are our friends. I am now going to close both threads in order to maintain the friendly, supportive and constructive environment MFK stands for.

Remember: It's not necessarily about being right, it's about inspiring others to do the right thing
HarleyK