Venustus Angelfish Won't Eat

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Hi, I bought a Venustus Angelfish from LA DD about a week ago. It didn't show a lot of interest in food at all. All it does is hide the rocks and pick them up. I wondered if any of you had any suggestions I tried mysis shrimps, reef plankton, brine, and strips of seaweed.I tried to soak the garlic and selcon food. I don't know what else to offer, because it never comes out, and when I see it, it's just in the caves that pick up the rocks. Is it possible that it's eating food off the rocks that I've added to the tank and could it live off just the food on the rocks? Any help is much appreciated.