Stegastes adustus reaches 15 cm. Oval uniform dark-brown body, juveniles with a blue ocellus on the dorsal. Extremely territorial: actively farms an algal garden on a coral or rock patch and defends it aggressively against all intruders, sometimes charging divers. Prefers shallow Caribbean reefs and rocks down to 5 m. Significant ecological role: protecting its algae delays coral recolonization.

