Water Changes

[LA321]

like the title said, anyone know how to calculate howmuch waterchanges to do on certain gallon sizes?

 

[Tolak]

Depends on a lot of variables, tank size, type & quantity of fish, & kind of filtration.

Tolak

 

[Monte20]

from what ive read here, the best way to go about it is to do it as percentages rather than figuring gallons. change 20-25 % of the water.

 

[freddyk]

Nitrates are an excellent way of guiding water change habits. When they get to a certain point (20-60, depending) then it's time. If this takes a week, or two weeks, it's a good sign to change the water. You really only need to test at first, till you have an idea of how the tank runs.

 

[qwikimpss]

A good rule of thumb but not absolute science is 20-25% once a week. Maybe less if your tank is planted because plants love nitrate. Theoretically on a heavily planted tank you could just top off evap if heavy metals wouldnt add up, but they would so that's shot!

 

[annka5]

There's a hideous formula for working out days worth of fish waste left in a tank if you maintain a given water change %age regime.
I got it from a website www.simplydiscus.com, somwhere in the "library" section. I don't have a link direct to it, though.

 

[CFC]

Test your tapwater for nitrates and then test your tankwater, if your tankwater reads within 20ppm of the reading from the tapwater then you are changing enough water and regularly enough. If your tankwater reads over 20ppm higher than your tapwater then you need to do larger water changes more regularly.

Some rough guidelines based on using suitable sized tanks are

Fish under 4 inches

light stocking of small fish change 10% weekly
moderate stocking of small fish change 15% weekly
heavy stocking of small fish change 20% weekly

Fish under 8 inches

light stocking of medium sized fish change 15% weekly
moderate stocking of medium sized fish change 20% weekly
heavy stocking of medium sized fish 25% weekly

Fish over 8 inches

single specimin with no tankmates change 20% weekly
single specimin with dithers and small clean up crew change 25% weekly
large fish community change 40% weekly

Specialised fish

African Cichlid community change 20 to 40 % weekly
Predatory fish (fish eaters) change 40% weekly
Sensative fish such as stingrays and discus change 25 to 50% weekly