There are eight known species of the Genus Heniochus, which is a member of the Butterflyfish family Chaetodontidae, meaning "bristle teeth" in reference to their prising snout and dentition. All eight species are similarly shaped with laterally compressed sides, a pointed rostrum and a lengthened fourth dorsal ray.
Of the eight species of Heniochus, two are common to the Red Sea: the Red Sea Bannerfish (Heniochus intermedius), and the Schooling Bannerfish (Heniochus diphreutes). The other species are the Long-Fin Bannerfish (Heniochus acumminatus), Pennant Butterflyfish (Heniochus chrysostomus), Masked Bannerfish (Heniochus monoceros), Phantom Bannerfish (Heniochus pleurotaenia), Humphead Bannerfish (Heniochus varius) and Singular Bannerfish (Heniochus singularius).
The Red Sea Bannerfish can grow up to 20cm and is found also in the western Gulf of Aden. It lives at depths between 3 and 50 meters, feeding on zooplankton during the day. These fish swim in pairs but are also found in groups of up to 24. Juveniles are found primarily at the base of reefs, living in larger groups.
In the Red Sea, these fish feed most actively at sunset and during the night, so divers may be less likely to see many Bannerfish in the daytime, as they may be hiding among corals.
The Red Sea Bannerfish appears to be a generalist feeder. It has been reported as a benthic feeder eating mostly sedentary polychaetes and some corals and other invertebrates off Eritrea, but as a planktonic feeder on larvaceans in the Gulf of Aqaba. It has a short gut, indicating that it doesn't eat algae and corals as much as some other butterfly fish species, but it is likely that it consumes some.
Schooling Bannerfish grow up to 18cm and are characterised by an elongated 4th dorsal spine. They have two black bands, the second starting behind the dorsal filament, yellow pectoral, dorsal and caudal fins, with a grey spotted snout and nape. They live along the reef front or external reef, in large schools swimming in mid water.
It resembles another Heniochus species, Heniochus acuminatus, but is smaller, with shorter snout, snout and nape spots lighter, and usually lives in large schools.
These fish are found not only in the Red Sea through to the Arabian Gulf, but are widespread also in the Indian Ocean. They inhabit depths from 1 to 210 meters, living in aggregations in the water column above the reef tops, feeding on zooplankton. Juveniles are found living closer to the bottom near reef patches, whilst adults spend the entire day in open water, protected by the schooling behaviour.
Schooling Bannerfish are typical Plankton feeders, with juveniles also acting as cleaners, feeding on parasites collected on other fish skin.