They get large. They eat ornamental shrimp when they get big. They graze on the rocks. Algae (marcro and film), sponges, tunicates, little worms. They may eat polyps of some kinds. Since they are pickers, they could go for clams, but, I did see a large Regal angel in Jim's tank before the disaster. Same kind of mouth, therefore, pretty much the same family as far as eating goes. Had a large Queen turn around and swallow a large banded coral shrimp in one bite one day. Maybe because he was hungry and the quarters were too small? Even a small one can graze all the live rock clean in a large tank. They will eat any fish food once they are used to eating prepared and frozen foods. Its funny to watch at first because they think they have to kill that frozen food first. Once they learn its frozen, they just turn into gobblers. I've had them with small fish. They are not fish eaters, normally. I believe there is a lot of misinformation about reef safe and non-reef safe fish in the well meaning sales oriented literature. I have 3 "reef safe" fish that eat coral like a coral eating butterfly. Have you asked the question on anyplace else?