For me it depends on what you keep with the firemouth. I have three of them in two different tanks. I used to have all three in one tank with my jack dempsey, salvini, and two blue acara. One of the firemouths kept terrorizing and beating up everyone. I moved him to a 30 gal with two convicts and now he keeps to himself. Usually you have to balance out the aggression with more aggression when it comes to firemouths.