Coral is not a problem with Harlequin Tusk. They are large wrasse, fierce looking but mellow. They do have small fishes and mobile invertebrates on the menu like CUC and small reef fishes and ornamental shrimpYou have your harlequin in your reef tank? What types of corals do you have?
Emperor and Queen are great species as I have them. Regals aren't very hardy. If you were to get them try adding all at the same time as the more dominant angel will kill the new one.Emperor angel, Queen angel, Passer angel, regal , angel, Looks downs, and clown trigger