Being an old diver, I strongly prefer a large tank (mine are all 8 footers, although 30 inches deep) with small fish which can act naturally as opposed to largish fish that make tanks look small. I love firefish, flasher wrasses, pygmy wrasses, dragonets (including weird ones like finger dragonets), yellow jawfish, etc. For me they are much more exciting and behaviorally interesting than tangs. If not a reef tank, dwarf angels are also nice active fish. But, keep in mind, I am a definite minority here. If a reef tank, one can add pipefish, etc. I have a 40 gallon refugium on both tanks so copepods are plentiful.