Mine doesn't seem that aggressive. Anything larger than about 2.5-3" he doesn't seem to consider food. There were 2 goldfish about that size that he seemed to ignore for a few weeks until I finally removed them due to bioload concerns. May be because he's obviously the biggest fish, he doesn't feel he has to defend territory or something. I don't think I've even seen him chase any of the other non-eatin' size fish in the tank in a long time. He sometimes attacks the glass and flares up, and likes to move stuff, but he mostly swims around watching people go by. If hands go in to move stuff he goes to the bottom, lays partly on his side and stares.