I can vouch for angels being nasty to benthic sharks. My LFS has a small (probably only 75-100 gallons) display tank where they put the larger show marine fish. They have a 12 inch bamboo shark and a gorgeous queen angelfish (among other things) and the shark is missing its left eye. Wasn't like that when they got it in, as I'm there all the time checking out the saltwater section. Its pretty sad, and I'm sure its the queen angel as the other inhabitants aren't nasty pickers.