The Titan Triggerfish, giant triggerfish or moustache triggerfish (Balistoides viridescens) is a fish is widespread in the Red Sea and in the Indian and western Pacific.
Populates coral reefs at shallow depths. It is particularly common in the lagoons of the atolls and in other environments sheltered by currents and undertow.
The titan triggerfish is diurnal and solitary. It feeds on sea urchins, molluscs, crustaceans, tube worms and coral. It often feeds by turning over rocks, stirring up sand and biting off pieces of branching coral. This is why other smaller fish species are often seen around it, as they feed on the detritus and smaller organisms that are stirred up. Titan triggerfish have been observed being aggressive to other fish who enter their territory.
It has the typical appearance of the Balistidae. The color is darkish in the central part of the body with a light caudal head and peduncle. On the eye and on the mouth there are two darker bands. The dorsal, caudal and anal fins are yellowish, brown or reddish with darker edges.
It reaches 75 cm in length.
Known for its territoriality, it becomes rather aggressive and violent if disturbed. Attacks to divers were reported by females guarding the eggs.