What are good fish to add to established tank

I have a small (30 gal.) mini reef set-up. This tank has been up and
running smoothly for over 1 year. There are the following in the tank:
caulerpa algae, 3 dwarf hermits, 1 pincushion urchin, 2 peppermint
shrimp, 2 dwarf feather dusters, 8 asst. snails, 1 neon blue goby, 1
red head goby and 1 blue damselfish. There is 35# of Lalo live rock,
also. I have a 3-way filtration system, compact flourescent lighting
and a small wave maker.
My question is, what fish could I add that would be compatible with
the present residents and conditions (lighting, etc.)? I would prefer
something that is easy-moderate in care needs.
Any suggestions would be greatly appreciated.
Thanks,
Angel