If there all about the same size Convicts are more than Capable of taking care of themselves too, have kept Convicts for years and have noticed they always seem to do better when there is 4 of them even though its stated to keep them in pairs. The convict is a very aggressive and evil fish though so don't try and keep anything like Rams with them though as they will just get whacked, actually be careful whatever you put with them as they proper evil little bastards even more so when they start breeding.