What sized tank and how long has it been set up? Having kept several angels over the past 10 years, I would never introduce one into a tank with no live rock. Angels are grazers and live rock can provide much needed nourishment. That said, offer it sponge based foods, frozen plankton, Marine Cuisine, Emerald Entree, chopped mussel and clam. Not sure how big the fish is now, but many times tiny juveniles don't fare well. Hopefully you have planned ahead for this fish. It will grow to the size of a dinner plate and be quite aggressive. A tank in the 180 gallon range is minimal for this fish.