Both are great animals. Regals are tough to keep. Seahorses requirements are much different from what angel fish need. Seahorses can be kept with more non-aggressive species like mandarin fish, gobies, fire fish, pipe fish, and file fish. I keep my seahorses with all these types of fish except for the filefish because I haven't found a pair of harlequin yet . Regals need a lot of room and seahorse can be kept in smaller aquarium. IMO I wouldn't keep the two fish together.