I've had a fish for a few weeks now, and the only thing he has eaten is bloodworms. He was the smallest fish at the store, and I thought he was just young. Now I think it might be because he is an extremely picky eater. I've tried three different types of pellets and some flakes with absolutely zero luck. He will, however, always eat bloodworms. I've tried waiting a couple of days (up to 6) without feeding him so he would get hungry, but he still spit the pellet out. Could there be an underlying problem? How long will blood worms keep him sustained?