How often do you have to do a complete water change?

Question

on a 20 gallon tank with a large goldfish, and a medium goldfish

with a filter

Answer 1

You should NEVER have to do a complete water change unless your fish all die from an ich outbreak or something. You should vacuum the waste off the bottom and do a partial water change (20-40%) once a week to once a month depending on the readings of your water and what the levels of your ammonia, nitrites and nitrates are. Changing 100% of the water in your tank destroys the beneficial bacteria colonies that are setting up an ecosystem in the tank that keeps your fish healthy and will change the chemistry of the water the fish live in too much. Not to mention you have to move the fish to do a complete water change and this stresses the fish and impairs their immune system. You should do some research on the nitrogen cycle in an aquarium. Check out the link below.

Answer 2

You shouldn't have to. Partial water changes every week are enough. With 2 goldfish in a 20 gal. (which is overstocked btw) About 40% once a week will help keep ammonia in check. Goldfish are very messy...

Answer 3

Ditto to Ghost Shrimp Fan
she hit the point exactly


EB

Answer 4

I agree with lashes but something else could help. Buy a snail or tw.. They help to clean the algae off the glass or the rocks if you have any.

Answer 5

well you see if u dont have a filter you will have to do it twice a month but if u have a filter you only get to do it once a month ... its good to buy a filter ... and your fishes will have a cleaner tank

Answer 6

if you have a good filter system in your tank,i would do one every 90days,if not do one at least every 30.