I had an adult emperor about 30 years ago. He was personable and ate anything frozen. FO tank, 125, had him for years until I went on vacation and my tank sitter killed everything with malation.

Saw one in an sps predomintate tank of around 220 gallons. 6 inch adult. It turned on the electric green trumpet and took several holes out of it while I was there. Then it hit an open brain hard enough to tear it. I think it was hungry at the time. The reefer fed it but it really didn't leave the trumpet alone after that. It left clams, mushrooms and sps alone. Overall I would have to agree with Cliff, keep an eye on them even after they are acclimated with clams and things. As a general rule with some fish; New clams that are stressed and clams in the sand bed are often targeted when clams up off the sand and in the reef are not.