Gobies (Gobiidae)
Small bottom fish perfect for the reef. Some species sift through the sand, others live in symbiosis with pistol shrimp.
Detailed explanation
The Watchman Goby (Cryptocentrus, Amblyeleotris) live in symbiosis with the pistol shrimp (Alpheus): the shrimp digs the burrow, the goby acts as a sentry.
Sand Sifting Gobies (Valenciennea) continually sift through the sand, eating microorganisms and keeping it clean.
Clown Goby (Gobiodon) live among the branches of Acropora and are suitable for nano reefs.