I have 20 *reef to be* and i really love sleeper/watchman(The kind that sifts sand out fo thier gills) gobies and there any species that i could put in my tank? I have about a 2-3 1/2 sand bed. could i get away with a diamond goby(prolly not)? Any info welcome

30pounds of live rock 25 pounds of live sand(or somewhere close to 20-25 puonds).