30 Gal - couple of clowns, some damsels and maybe one pigmy angel.
try alot of interts - star fish, crabs, feather dusters, mushroom polyps and keep the fish to a minimum. that way it's like a reef echo system vice a fish tank!
You could even think about some urchins - they are neat - fire urchins are inexpensive and they roam about the whole tank dya and night.
I have one and plan on buying another.