Beginner fish: Royal Gramma, Bicolor or Flametail Blenny, Percula Clown, Blue/green chromis
Beginner inverts: Cleaner shrimp
Should never be in home aquariums: jellyfish, parrotfish, sharks (IMO), stonefish, octopus.
Expert Only: Achilles Tang, Lookdown, Batfish, Filefish, Cowfish