Yeah, those are pretty angels. Basically all angels are possible clam and coral nibblers. Usually only the pygmy angels do ok in reef tanks and even then if varies from fish to fish. If you really want both, I would keep them in separate tanks out of fear of losing a beautiful clam! I think it is just a roll of the dice whether it will pick on the clam or not. Perhaps if you keep the angel well fed and do not include any clam in any of its food (sometimes found in frozen foods) it will not bother with it.