Angelfishes for Marine Aquariums: Diversity, Selection & Care

Amongst all families of marine fishes, the Angelfishes rank supreme for splashy color, markings and interesting behavior. Do you think that fishes are intelligent? I believe some like the Angels are; knowing of their own existence, remembering their territories, and at least some forming pair bonds and haremic associations; apparently for life. For saltwater aquarists, marine Angels span the breadth of "usability"; with some being small enough to be placed in nano-reefs, to others requiring systems of a few hundred gallons as adults. There are Pomacanthid species with more specialized nutrition needs; ones that feed mostly on sponges in the wild; others are more generalized planktivores, the majority omnivorous period. Similarly, some species are "hard as nails" given appropriate aquarium care, while other Angel species historically have historically fared very poorly in captivity.