Mine just refused to share the bottom of the tank with anyone else. He's bitten a few fish larger than him, but the only thing he's brutally killed was a Red Tail Catfish that had a good 3-4 " on him. I used to keep him with my larger fish (arowana and Odoe pike) but I've since moved him to a tank by himself, and he's actually a bit more personable than he was in the presence of other fish.