Not the best diet plan in the world for him, but I've got a common that currently goes nuts for a beefheart/shrimp mix I feed the other fish in the tank. He still gets fresh veggies and algea wafers regularly, but homes in and bullies the other fish away from the beef. He'll also take raw shrimp in the shell, earth/meal worms, and has a thing for crickets. (He's stolen more than a few crickets right out of the mouth of other fish.)