howdy!
i have a 7 gallon bowfront nano
as a rule, you can keep one small fish. There is a forum specifically for seven gallon bowfront tanks (if that's what you have), it's a really great info source to see how wonderful everyone's nano reef is.
I've only seen one, and at most, two fish in seven gallon tanks. Usually one fish is a clownfish. I've also seen a six line wrasse, a fire fish *thinking here* and sometimes just corals and an anemone or two. Everybody seems to have at least one shrimp.
My tank is still cycling so I can't be much help, just tell you what other people have.