I am currently running a 30 gallon FOWLR tank with a rena filstar xp1 filter. I have 2 strong powerheads and a Seaclone skimmer. Currently my livestock consists of 2 percula clowns, 1 banggai cardinal, 1 cleaner shrimp, 1 camel shrimp, and 6 hermit crabs. I would like to add a royal gramma and a pajama cardinal. Does this sound ok? Am I able to add anything else? Are snails a must? I would appreciate any and all feedback. Thanks