Opinions please on large water changes
- Thread starter beerad555
- Start date
From 1981 Thru 1990, I only added water. To make up from evaporation. On all of my aquariums. Did not have Internet back then. To know any better.
Never killed a fish until I tried a salt water tank in 1991, and learned the expensive way.
I admire your honesty, I was doing things also years ago that would be frowned upon today. TFH magazine's, and working around knowledgeable people helped, but lol still learning .
I never change more water than I have to, for example if I have a shoal of 12 tiger barbs in a 30g, I'm not going to change 99% for the sake of it, when they'd probably do just fine with 20%.
As long as you're controlling your nitrates, that should dictate the water volume you change. A further factor in large water changes is risk, if you change 90% of the water and your water company have made an error, you can potentially lose all stock.
Conversely, if you do 20% changes for example (and it controls nitrates), you might be able to avert disaster.
As long as you're controlling your nitrates, that should dictate the water volume you change. A further factor in large water changes is risk, if you change 90% of the water and your water company have made an error, you can potentially lose all stock.
Conversely, if you do 20% changes for example (and it controls nitrates), you might be able to avert disaster.
This is why you really need to set up a "system" to make water changing a breeze. If it's easy and near effortless, you will be inclined to do it more often. If you're doing via the 5 gallon method, chances are, water changes will be a tedious chore.
Well I don't have the monster stocks that most people do in a 125. I have larger community fish for my mainstay. I can go 2 to 3 weeks without too much of an issue as I prefer to use algae in my tank to help with nitrates. Just as long as it's not the blue green variety. If I do that I increase the wc's for a few weeks after. That being said, my wc's are 30% weekly or I'll increase to 50% for 3 weeks when I've gotten lazy. And I gravel vac until there's nothing coming out of the gravel. And my fx5 gets cleaned every month because it's slammed with media and it gets filled with nasty-ness at about the 35 day mark. Reducing flow and not allowing air to pass through for its purge cycle.
I done a few threads on this...
These are the results assuming tank maintenance are up to scratch, basically what your nitrates creep to before they level out...
i wont go into the maths side of my other post but it ended like this;
25% water change = a settled nitrate level of 3.75 x your weekly produced nitrate for ever if you only do 25%
50% = 2x
75%= 1.35x
So if your heavily stocked and go from 0 to 50ppm in a week and only do 50% yes your settled nitrate is 100ppm.
25% is close to 200ppm!
These are the results assuming tank maintenance are up to scratch, basically what your nitrates creep to before they level out...
i wont go into the maths side of my other post but it ended like this;
25% water change = a settled nitrate level of 3.75 x your weekly produced nitrate for ever if you only do 25%
50% = 2x
75%= 1.35x
So if your heavily stocked and go from 0 to 50ppm in a week and only do 50% yes your settled nitrate is 100ppm.
25% is close to 200ppm!
Sod it, heres the math, this should be sticky Imo...
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
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
