My 12" Aussie Jard lives with 2 10" Peacock Bass (Temporary), a 12" Oscar, 7 3-4" Silver Dollars, 2 Synodontis, 1 Bullseye Cat in my 180....I have very little agression issues and the majority are between the catfish. I agree that it depends on the fish, but also depends GREATLY on how they are introduced to the tank.