i used to have a 5" one it was mistaken for a green severum, he was not very colorful but damn was he aggressive, he was 5" tried to take out every thing in my tank, that included: a 9" jag a 9" severum and a 7" sev and a giant gourami. so i sold him and he is living in a 6x2.5x2 tank with 5 oscars who are all scared of him lol. but they are a nice fish and mine would only live with my silver arow and my catfish. he liked to be the only middle dwelling fish, but i think if you had more tham on they will be ok in a large enough tank.