Not research, but my experience with the captive bred regal angel is that I've seen them nip at my acropora early on but have now lost interest in them likely due to getting used to my feeding routine for the tank. My acros have good polyp extension during the day time but I'm sure the extension could be even better and longer. Forgot to mention, but I also have a squamosa clam that the angels don't bother. Keep in mind, my regals are still <2"