Yellow Citron Goby (Gobiodon citrinus)

Citron Gobies spend their entire adult lives inside a single Acropora colony, wedged between the branches and rarely straying more than a few inches from home. They coat themselves in a mucus layer that's mildly toxic, useful against predators, though a stressed or dying goby can actually harm the coral it lives in, which is either an unfortunate design flaw or a reminder that even reef partnerships have fine print. Small, bright yellow, and endlessly entertaining to watch dart in and out of the coral branches.

Care level: Moderate · Temperament: Peaceful · Max size: ~1.5" · Min tank: 20 gal, with Acropora coral · Diet: Omnivore, coral mucus + meaty foods