The Pennant coralfish or Coachman, Heniochus acuminatus, is a tropical fish of the family Chaetodontidae. It is also known colloquially as the “poor man’s moorish idol”.
The fish is mostly black and white with an elongated dorsal fin making the fish reach around 9.84 in (25 cm). The fish’s caudal, anal and pectoral fins are most commonly bright yellow. It is very similar in appearance to the closely related Heniochus diphreutes, but has a longer and more circular shape.
The species are social fish, and found in pairs or in shoals. They are a very passive fish, and rarely territorial. Some individuals even act as cleaners, especially when young, by removing parasites from other fish.
The pennant coralfish eats mostly plankton in the wild but are omnivorous in an aquarium setting.
The pennant coralfish’s natural distribution is in the Indian and Pacific oceans in reef settings, from southern Japan to Micronesia and Lord Howe Island. It is also found in the Seychelles.
It inhabits deep, protected lagoons and channels, and the deeper parts of outer reef slopes.
The fish is uncommonly harvested for anything other than the marine aquarium industry. It is a fish commonly sold as an alternative to the Moorish idol, which are considered to be nearly impossible for most hobbyists to keep. It is fairly easy to care for when maintained in a properly-sized aquarium with peaceful tankmates.