In our 12 gal we have:
1- True percula clown
1- Goby Firefish
1- small 6 line wrasse (when he out grows the tank he will be moved-currently small in size)
25- Banded Trochus snails
5- blue leg hermits
Pseudochromis or Royal gamma is fine. Jaw fish, Chromis, most goby's or Blennies.