I have ket the following Angels in my reef tanks with the following results:
Flame Angel: I kept this fish for over a year in two different reef tanks. First was my 240 gallon. This tank has SPS, Clams, Zoanthus, and LPS. The fish never touched a single coral or clam. Then I moved her over to my Elos 70 (55 gallons). In this tank I had SPS and LPS also. Again she never touched anything.
Potters Angel: I obtained this fish at the same time as the Flame. He was in the same tanks with the same corals. Again this fish never touched a single coral or clam.
Majestic Angel: I had this fish for several months before I took the 240 gallon reef down. She was as safe with corals as my flame and potters. I never saw her touch a single coral or clam. The only think that she ever picked at were the barnacles and mussels that were in the rock work.
Regal Angel: I had this fish for over a year and a half. She was in the 240 and the Elos 70. This was the most "reef safe" fish that I have ever had. Ive had clown fish that were more abusive to corals than this fish was.
Blue Face: Ive kept this Juvenile 1.5" fish in an Elos Mini for several months. She is in the tank with LPS and Zoanthus. The only coral that she has ever taken a likin' to was an aussie elegance coral, which she ate.
Bellus: No issues.
IMO the key to keeping angels off of corals, is to feed often and keep them preoccupied. I feed my tank 4-7 times per day. In my tanks with angels I feed on the higher end of the scale. These fish feed almost constantly in the wild, and when we bring them into our tanks, they forage just as they do in the wild. If you look at Centropyge angels, they constantly nip at the substrate/rockworks/anything in their path. It should be expected that these fish may nip at corals. But typically the nipping is only enough to irritate the coral, not kill it. I have noticed that many times centropyge angels will nip at a coral, move on past, and come back several minutes later to consume the mucous that the coral secreted in response to the nipping. They dont typically eat the coral flesh, just the secretions.
Also, if you keep the fish "entertained" they are less likely to pick at corals. I have seen some tanks with large angels that look restless, and as such they pick at corals. I do not believe that this is the fish desiring to eat the coral, as much as it is the fish just nipping out of "boredom". I know I am using human terminology for fish, but I think it works.
IMO the best way to preoccupy fish is by adding other similar fish. For example, multiple angels.
These are just my observations, I may be totally incorrect. But frequent feedings, and preoccupied fish has worked for me.
~Michael