Fish

Titan triggerfish

Balistoides viridescens

The largest reef triggerfish of the Indo-Pacific. Give nesting fish a wide space, and if you are above a sand nest, swim away sideways and low, never straight up.

Least ConcernIn 40 Atlas countries

Least Concern (IUCN, 2022) means it is not at high risk of extinction worldwide today.

Titan triggerfish swimming over a reef slope in blue water — Photo: fletchermoore, iNaturalist, CC BY

Titan triggerfish above coral and sand in the Maldives — Photo: Darren Obbard, iNaturalist, CC BY

Titan triggerfish turning over coral on Norman Reef — Photo: Michael A. Alcorn, iNaturalist, CC BY

Titan triggerfish feeding on the reef in Komodo — Photo: R Vasconcellos, iNaturalist, CC BY

Close view of a titan triggerfish face and teeth — Photo: cello caruso-turiello, iNaturalist, CC BY

Photos show the species, not always the places on this page.

Length

Typical adult size not well measured, and most fish seen on dives are smaller; largest recorded about 75 cm (2.5 ft)

Weight

Not reliably measured

Next to a person

The largest are about as long as a person's lower leg; most are smaller

What it eats

Sea urchins, crabs and other crustaceans, molluscs, tube worms, and small clams it digs out of dead coral rock.

Around people

Potentially dangerous, respect

How it lives

The titan triggerfish flips rubble and breaks dead coral rock to find food, and other fish often follow to pick up scraps. It lives alone or in pairs. The female, sometimes with the male, guards the eggs in a shallow sand nest and can charge and bite divers who come too close. Its jaws are strong enough to crack shells.

Where it goes

Resident. It stays on its home reef all year, and in the nesting period it defends a small area around the nest. No migration is known.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

Found from the Red Sea and East Africa across to the Line and Tuamotu islands, and north to southern Japan, but generally not in Hawaiʻi. It lives from the shallows down to about 50 to 60 m, depending on the source. At Fuvahmulah, Maldives, at a site where tiger sharks are fed for tourism, titan triggerfish started all 10 recorded fights with tiger sharks in 2024, and the sharks swam away every time.

Meet it respectfully

Never chase, feed or crowd a titan triggerfish, and never follow a nesting fish for a photo. Watch for sand nests and a fish facing you with its back spine up. The guarded zone is often described as an upside down cone above the nest, so swimming up can keep you inside it. Swim away low and sideways, out of the cone, keep your fins or camera between you and the fish if it charges, and do not go back. Nesting is linked to the moon, but sources do not agree on which phase.

Fun fact

Tap the bulb to light it up.

Sources for this page

Facts checked 26 September 2026. Photos: Unsplash licence, or Creative Commons as shown on each photo.

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