Mine wasn't shy at all, he was definitely the king of his tank. He was very interactive, always out and about with LOADS of personality. He was a picky feeder when I got him, feeding fresh mussels, having seaweed on a clip all day and adding garlic to everything helped to develop his appetite. He died suddenly after about nine months, he was fat and happy looking, with no sign of disease. They're difficult fish with a lousy survival rate. IME when an angel starts hiding and refuses to feed, it's a very bad sign. Try offering him some fresh, meaty foods and keeping the environment as stress-free as possible, hopefully he'll come around.