Sigh. I came home tonight and discovered that the yellow tang in our aquarium had nipped to death a beautiful hard coral, most likely a bird's nest. Where once there was brilliant pink, now there is only bone white. I had thought that tangs were reef safe. A quick consult with the fish book says "may nip at corals if underfed". I had been starving this guy to force him to eat some of the nuisance algae in the tank... d'oh! Another expensive aquarium lesson learned...