This is from Bob Fenners web site....." Angels are separate sexes, though some (Centropyge, Genicanthus) are protogynic synchronous hermaphrodites (first females turning into functional males). Spawning, either in pairs or in "harems" is environmentally cued by light, temperature, other organism's activities. Gametes released into the water column, result in some planktonic larvae; developing and settling at the whim of currents.
Some species have been tank "bred" utilizing hormonal manipulation. Young have been tank reared for Pomacanthus, Centropyge and Genicanthus species. See Thresher for details."