I'd say 1-2 if you plan to put more fish in there. Discus usually require 10 gallons a piece as a rule of thumb - but if you're going to put that filter on it you might be able to push 3. If you plan to get any other fish for the tank - corys, cardinals, rams, etc. I'd say 2 - but if you're doing just discus with frequent water changes you should be ok with 3. |