Why not go a pair of cons and an oscar? I have a very larger oscar with a JD, texas, GT and a breeding pair of convicts in a 180G. Like others have said my cons have their own little hiding spot where they breed. They don't let any other fish come near but they don't go out hurting others either. They just keep them away. I find them very interesting to have in my 180G tank and watch the way they protect their space against my larger cichlids.