Bannerfish belong to the genus Heniochus. They are a type of butterflyfish, making them part of the Chaetodontidae family. There are at least eight known species of bannerfish: pennant coralfish (or longfin bannerfish), threeband pennantfish, false moorish idol (or schooling bannerfish), Red Sea bannerfish, masked bannerfish, phantom bannerfish, singular bannerfish, and horned bannerfish. All species of bannerfish are marine fish. They are found mostly in the Indian and Pacific Ocean, or Indo-Pacific, depending on the species. They are very prominent in the Red Sea. They prefer the shallows of coral reefs, but some adult species will spend the day in open water. These fish may be spotted in pairs or in large schools. Some species may be found anywhere between 1 and 210 meters deep. Like other butterflyfish, the bodies of bannerfish are small and laterally compressed. As the family name Chaetodontidae suggests, “bristle teeth” is used to describe their prising snout and dentition. Their snouts are elongated for prying. Bannerfish always have white and black colors, but depending on the species, they may also have yellow or brown patterns. They have at least one or a few wide vertical stripes on their bodies.
Their diet consists of coral polyps and hydroids, small invertebrates like polychaete worms, and sometimes zooplankton. Some species of bannerfish are generalist feeders. The Red Sea bannerfish is a benthic feeder off Eritrea, and a planktonic feeder in the Gulf of Aqaba. Some bannerfish, like juvenile schooling bannerfish, will act as cleaner fish that get rid of parasites off of visiting fish species. Bannerfish are very territorial. The pairs will spend the late afternoon defending their territory’s border and challenging other fish of the same species. These territories usually have a coral centerpiece. It seems bannerfish of the same genus, but a different species, are allowed to pass through a different territory freely. Like other butterflyfish, bannerfish are a welcome sight for both divers and aquarists. According to the International Union for Conservation of Nature (IUCN) Red List, bannerfish appear to be of least concern in terms of endangered status for now.