My brown bullhead is about 10 inches. He's very territorial and will hammer anything that gets near him. He routinely latches on to my huge American Eel, and has gotten hold of my LMB. He always lets go before it gets crazy, but he does not put up with drive byes. That said, I almost think he just tries to eat anything that gets near his mouth. Once he realizes it's too big, he lets up. He's destroyed 3-5 inch comet goldfish though... several times. He hangs out in a log and the comets go there to hide from the Bass - as soon as they get in front of him he wastes them. I wouldn't keep smaller fish with him because he's such a jerk... but smaller fish wouldn't survive the bass to begin with so......