I've had all 3 Firemouth, Black Convict/Zebra and Jack Dempsey's in the same aquarium at one time. If you get them when their small it usually works best. The Jack Dempsey's will get larger than the Firemouths and Convicts as the fish get older and you may run into some problems then. Also the Convicts spawn a lot and get pretty aggressive guarding eggs and fry. You'll need a large aquarium with plenty of structure to keep all 3 species together in.