How much live rock is in there? There are a few small breeds of fish that will work in there such as a clown goby, sharknose goby, neon goby, blackray shrimp goby, whiteray shrimp goby, firefish, one chromis, one clown. Go for fish that are not territorial and stay small. Pick one mid swimmer and one bottom dweller. Don't add them both at once, space them at least a month apart.