Heniochus diphreutes
Small black-and-white schoolers found from the Maldives' Central Atolls to Queensland reefs, year-round in warm 22-29C water.
A small, disc-shaped butterflyfish around 14 cm, boldly banded in black and white with a trailing white filament off the dorsal fin that streams behind it like a pennant. The yellow patch behind the head and the long snout help separate it from plainer black-and-white reef fish, and it is almost always seen in loose groups rather than alone.
Look for it hovering in loose, drifting schools over reef slopes and drop-offs, often well off the bottom in open water rather than tucked into coral. It picks plankton out of the current with unhurried, almost lazy movements and generally ignores passing divers, making it an easy, calm subject for mid-water shots.
Juveniles of this species will sometimes pick parasites off larger fish, a cleaning behaviour unusual for a butterflyfish and one that briefly turns it from planktivore into reef cleaner.
Comfortable across a warm band of roughly 22.4 to 29.1C, so it is present on tropical reefs year-round with no strong seasonal pattern detected in the data.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged in the Maldives, especially the Central and Northern Atolls, with strong numbers also in the Philippines (Luzon, Palawan), Indonesia, Queensland in Australia, Thailand and the Egyptian Red Sea. It turns up across a wide depth range, from shallow reef flats down past recreational limits, so it shows up on both easy reef dives and deeper drop-offs.
Mapping where Schooling Bannerfish is logged…
The Maldives is the strongest area, particularly the Central and Northern Atolls, followed by the Philippines, Indonesia, Queensland in Australia, Thailand and Egypt's Red Sea coast. It is logged as uncommon to common at most of these sites rather than guaranteed on every dive.
There's no strong season in the data, and with a comfortable range of about 22 to 29C it's present on tropical reefs all year. Any time you'd normally dive the Maldives, Philippines or Great Barrier Reef works.
Look for a small black-and-white banded butterflyfish with a trailing white dorsal filament, usually in a loose group hovering above the reef. The yellow patch behind the head and the schooling habit are the quickest giveaways.
They stay small, typically around 14 cm, which is modest even by butterflyfish standards.
Young individuals occasionally act as cleaner fish, picking parasites off larger fish, a role rarely seen in the butterflyfish family. Adults are more typically seen plankton-feeding in mid-water schools.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Foureye Butterfly Fish
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