Schooling bannerfish

The schooling bannerfish (Heniochus diphreutes), also known as the false moorish idol, is a marine ray-finned fish belonging to the family Chaetodontidae. This species is commonly found in the Indo-Pacific region.

Measuring up to a maximum length of 18–21 cm, the schooling bannerfish is a relatively small fish. Its body is laterally compressed, and the first rays of its dorsal fin extend into a long white filament. The fish displays a white background color with two prominent black diagonal bands. Additionally, its dorsal, caudal, and pectoral fins are yellow beyond the second black stripe. The head of the fish is white, with black eyes connected by a black to gray band. Its short snout is spotted with black to gray, housing a small terminal, extensible mouth.

The schooling bannerfish can be found across tropical, subtropical, and temperate waters of the Indo-Pacific, spanning from the eastern coast of Africa (including the 🌊 Red Sea) to Polynesia and Hawaii (🇺🇸 United States), as well as from southern 🇯🇵 Japan to the Kermadec Islands in 🇳🇿 New Zealand. This species tends to favor external reef slopes and channels, exhibiting a broad depth range. While it is commonly observed at depths between 5–30 m, it can also be found as deep as 210 meters in certain locations.

This particular fish species lives in large groups, as implied by its common name. Its diet mainly consists of zooplankton in open waters, and juvenile individuals have been observed acting as cleaner fish, a behavior also exhibited by adult bannerfish. When it comes to reproduction, the schooling bannerfish forms pairs. Notably, there have been documented instances of this species cleaning parasites off the short sunfish (Mola ramsay) near the 🇲🇻 Maldives.