My Moorish Idol eats everything i put in the tank (flake, kelp flake, nori, mysid, pellets, marine mixes, etc..), but he continues to loose body weight. Even though i feed him 4 - 5 times a day. I understand there needs for sponges, bryozoans etc, but i've heard about feeding moorsih idols living in tanks for years. What can i feed him that will fatten him up?