They would probably work best in a 55 gallon tank although I've known some that have kept them in 29's. They are really cool fish, just slightly on the mellow side but can be aggressive towards mellower fish. I accually think they can be bullies but only if the fish is really mellow otherwise mine was always getting his butt kicked. He kind of liked to dish out the attitute but didn't have the goods to back it up lol. They are a really cool fish and my large male (8 inches) just passed a few months ago. I think he was really old. I would raise another 1 in a heartbeat. I would probably keep them with some Archocentrus like a sajica. Maybe a severum. Not an overly aggressive fish. maybe just alittle bit of a troublemaker. If you have the chance to get 1 you should go for it.