Pygmy cherub angels are perfect for any reef. Active, hardy, small, and don't bother anything. I have had one for two years. I have also had a Lemonpeel angel in the same 55 gal set-up. I cannot keep polyps (except GSP), Brain Coral, Gorgononians or Xenia because it pecks constantly at them and they won't open up. Therefore the coral in my tank is limited because of it. It's a beautiful fish, though, and luckily I have other tanks I can keep these corals in.