I have a fluval evo 13.5. I have had it set up for 3 months now. I had 2 green chromis in it but have taken them out to hopefully put a pygmy angel in the tank. The angelfish is about an in ch maybe an inch n a half in size and lives with many corals with no problems with nipping on them . Is it OK to put a pygmy angel in a nano tank is my question?