I have been really happy with my Orange spotted Sand Goby/Diamond Goby (From Red Coral) as he sifts the sand but does not bring it up onto corals.
Also consider a Wrasse as I LOVE my wrasse - very active, very striking, lots of personality and an easy, hardy fish!
I have these in a 27G, no sump with 2 clowns and alot of coral and I am fully stocked - having nitrate issues, so I wouldn't add anymore to my system. However the sump would help and a YCG is a very small addition to the bioload.
Good Luck with your choice!
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Red Coral Online Store 
www.redcoralaquarium.net
45 Gallon Cube with 10 Gallon Sump, Lighting 8 bulb T5, Vertex IN 80 Skimmer
-2 Occelaris Clowns, Engineer Goby, RBTA, Peppermint Shrimp
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