I have a 28" jiar in a 270gal (3'x6'). I can't tell what he lives on. I have 2 marble cats, and a red tail with him now. The only thing I've seen him eat is frozen blood worms. He doesn't even seem to like worms now. The cat fish are intimdated by him. I took a 28" shovel nose and an 18" pictus out to my newly set up 480gal (4'x8') tank thinking they were a problem. He seems to be healthy. I figure he will eat when he gets hungry enouph. I'd like to see some eating aggression though. I have a 14" jar in a 110gal tank. He eats any thing with gusto.