How many water changes should i do each week? What percentage?

[Maxp123]

I have a 20g with 6 cherry barbs, 8 cardinal tetras, 4 corydoras, and 4 otocinclus. My tank is a 20 long if that matters. I have plenty of anachoris in the tank with one, hugely-horrendous lily bulb

 

[Terrance]

One 50% water change every week.

 

[absolutangel04]

Do you have a test kit to measure water params? That can help you figure out a pwc schedule. If not, the 50% suggested by Terrance is a good idea.

 

[BHead707]

i personally do 2-25% changes a week but thats just what i like to do

 

[joy13]

You will need to watch your ammonia and nitrates with that many fish you may end up doing several small ones a week. Is your tank planted?

 

[Maxp123]

One of the first things i said was the plants in there. My perams are non-existent at the moment (even though my tank is cycled

 

[Terrance]

Your water kit only measures ammonia/nitrIte/nitrAte. The nitrAte helps us measure the amount of dissolved organic waste and other pollutants (something you cannot measure with hobby test kits) in the water. The plants may or should remove significant amount of nitrAte if growing well. If you don't know how much nitrAte your tank produces, then there is no way you can tell how much total pollution is in the water. Whether a tank is planted or unplanted, water changes should be done every single week (50% highly recommended). Both fish and plant benefit from the water change. There are nutrients from fresh water that plants need. You replenish the needed nutrients if you change the water. If you're depending on your water to buffer your water, then water changes are even more important because kH is lost through time.

edit: I wrote the same thing twice..