nitrate-water change relationship.

[justarn]

Hey all, heres something ive been thinking about recently, not sure if its been covered before.

get your maths head on haha...

i was randomly throwing some figures about and this should help people understand how much water should be changed weekly...

firstly for the sake of the calculations we will assume tap water is 0ppm, the maths gets alot more complicated otherwise!-) here in the uk its more like 40ppm out of the tap, and obviously the americans are blessed with less than 10ppm!-)

lets say you have a 100g tank with a 12 inch oscar that creates 20ppm nitrate (estimate) in 1 week

so first one;

50% water change per week

week 1 = 20ppm ( oscar waste)

after water change = - 50% = 10ppm

/\ get the idea?

week 2 = 30ppm - 50% = 15ppm

week 3 = 35ppm - 50% = 17.5ppm

week 4 = 37.5ppm - 50% = 18.75ppm

week 5 = 38.75ppm - 50% = 19.375ppm

week 6 = 39ppm -50% = 19.5ppm

week 7 = 39.5ppm -50% = 19.75ppm

week 8 = 39.75ppm see it slows down,,,

so at here it flattens out and as you can see at a 50% weekly change you end up with an end of week max nitrates of 2x your fish's weekly produced nitrates.

if you miss a week and then continue doing your changes evry week it will gradually chase back down but you can see the importance of regular large water changes when keeping large fish in tight quarters.

heres at 25%

week 1 20ppm -25% = 15ppm
week 2 35ppm -25% = 26.25ppm
giving up on the maths here a bit but you get the idea
week 3 46ppm -25% = 34.5 ppm
week 4 54.5ppm -25% = 40ppm
week 5 60ppm - 25% = 45ppm
week 6 65ppm -25% = 49.75ppm
week 7 70ppm -25% = 52.5ppm
week 8 72ppm -25% = 54ppm
week 9 74ppm -25% ect ect

25% per week gives you 3.75 x your weekly bioload before your weekly water change.

75% water change per week per week

week 1 20ppm -75% = 5ppm
week 2 25ppm -75% = 6.25ppm
week 3 26.25ppm -75% = 6.50625 (maths without a claculator if this is wrong lol)
give up on maths again haha
week 4 26.5ppm -75% = 6.512
week 5 26.512 = ect ect

so 75% water change per week keeps you at weekly max of about 1.35 x your fish's weekly produced nitrates

summary

75% pw = 1.35x your produced nitrates max
50% pw = 2x your produced nitrates max
25% pw = 3.75x your produced max

i would like this to be tidied up and made sticky if possible, this needs to be common knowledge imo.

also could someone confirm what nitrates an average 12 inch oscar would produce in a 100g as i actually have no clue, sorry if this is miss leading.

also if anyone else has examples of nitrates produce by single or groups of fish please add your info, remember to add tank size and fish size. only if you actually know your weekly nitrate max figure before a water change tho, we dont need this being filled with bad info.

if im totally wrong please feel free to correct me and i will eat my own head lol....

 

[JK47]

You are not taking into account the fresh water going back in without nitrate.
50% out leaving 10ppm nitrate replaced with 50% water containing 0ppm nitrate will leave 5ppm.

 

[justarn]

Cheers jk, so is it as simple as halving the results or do we need to recalculate the whole lot? Too late for me now in the UK!

Any idea on the waste of a 12 inch oscar in a 100g?

 

[justarn]

Anyone else think this is vital info that is not common knowledge?

 

[duanes]

I have found by doing a 20% to 30% water change every other day (often every day in summer), I can keep my nitrate level between 2-5ppm on all tanks.
I have about 1500 gals of tanks in-line on 3 sumps, and find its much easier to do smaller water changes, more often while just sitting and watching the fish, than trying to do large changes once per week.
In summer old water is sent directly to the garden with the turn of a valve.

 

[Tifftastic]

I'm honestly curious as to how you manage 40 ppm out of tap in the UK. After my meeting today it looks like I'm staying to do a PhD and want to start a tank again (my first year here has been in halls).

Also, I *think* cutting all the results in half should work. I don't have much experience with keeping Oscars so couldn't tell if you are right or not. But it is also going to matter how much food you're feeding, how often, quality, algae build up (algae eats nitrates), filtration etc. It makes sense to me to make it an arbitrary number so that it can be used as an example but not a definite rule.

 

[justarn]

So....
Week 1
20ppm -50%= 10ppm %50 dilution =5pm
So before water change take 20 off for post water change.
End of Week2
25
End of Week3
26.125
End of Week 4
26.5
End if week 5
27.250

So im guessing 50% equals 1.5x produced nitrate. Thats much better!-)

 

[justarn]

Thanks tiff, its not in half, its 0.75 of the result on 50%, assume its similar on the others. ive had a few too many drinks tonight to go through it all, its 11.20pm here lol....
As you said food matters, need a constant of feeding twice a day for 5min, all the fish will eat plus netting out Un eaten food and regular maintenance.

 

[justarn]

As far as managing 40ppm we just do the same as you unless we have rays or discus or similar fragile species. Then we need hma or ro with added minerals... Our tanks suffer the fact that we keep as close to our tap water as we can.... The lfs do it, hell we all do.... I know anything Above 20ppm can effect fish, its just something we do here. UK fish are lucky to get someone that cares, the people in the USA who slack run their tanks at 50-100ppm would be the same as our slackers at 90-140ppm... Aside from the nitrates our water is pretty good from my research though, good minerals and we dont use cloramine as far as I know, just clorine, water in my area is very hard tho.

 

[Tifftastic]

Interesting, the way I have it is
Week one: 20 ppm produced - 50% removed = 10 ppm * 0.5 dilution = 5 ppm

Week two: 5 ppm + 20ppm produced = 25 ppm - 50% = 12.5 ppm * 0.5 dilution = 6.25 ppm

Week three: 6.25 ppm + 20 ppm produced = 26.25 ppm - 50% = 13.125 ppm * 0.5 dilution = 6.56 ppm

Week four: 6.56 ppm + 20 ppm produced = 26.56 ppm - 50% = 13.28 ppm * 0.5 dilution = 6.64 ppm

And so on . . .