Opinions please on large water changes

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That's why everyone with large cichlids in minimum sized tanks needs to be doing fin level, you fish will thank you with great color and massive growth.
 
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justarn said:
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
Click to expand...
Excellant info thanks.
 
I think some people might think their impossible to decipher orange red nitrate tests at 20 ppm are not going up that fast. Until their in the 120ppm range.
 
I do 75% WC weekly for my heavily loaded 125 and 75 show tanks. I would like to do 95% WC if I could, but I need to leave a few inches of water to cover my fish. Setting up the WC and siphoning the substrate is 95% effort, draining and filling the tank takes time but is only 5% passive effort, so why not do more. I employ double hoses to speed up the draining time.

I can do large WC and get away from it because my tap water is chlorinated only. I just throw in dechlor and fill the tank directly from the tap. Be careful, if your tap water is chloramined, there may be safe limit of how large a WC you can do. Please chime in.

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justarn said:
That's why everyone with large cichlids in minimum sized tanks needs to be doing fin level, you fish will thank you with great color and massive growth.
Click to expand...
Taking the water level down to the fishs' dorsal fins
 
markstrimaran said:
It gets easier than just continuous dripping.
Click to expand...
What's easier than continuous drip? I change filter cartridges every 3 months. I do a nitrate test every couple months "just to be sure".
 
You need to turn over alot more water on a drip due to dilution tho right? About 150% per week, maybe more? I'm on a water meter and that would be very costly to me...
 
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