The long fin bannerfish Heniochus acuminatus, is also known as the coachman or pennant bannerfish and is sometimes called the poor man’s moorish idol by aquarists as they are more affordable. They are close relatives of the butterfly fish, being in the same Family, Chaetodontidae.
Longfin bannerfish have a white body with two black oblique bands, yellow dorsal, tail and pectoral fins and a straight black line between the eyes. The dorsal filament which is white grows as the fish matures and trails behind the fish when it swims. Juveniles and adults are very similar to each other. Many people confuse them with the schooling bannerfish Heniochus diphreutes which is slightly smaller with a slightly differently shaped body. They also have a triangular band between the eyes instead of the straight line on the longfin bannerfish and this is the quick way of distinguishing between the species. The longfin bannerfish can grow up to 25 cm in length and are attractive looking fish. At night their colors darken and they go a dark grey color on the white bands. Once a light is put on them they quickly change back to their daytime colors. The process takes around a minute.
They are very friendly fish and will often approach a diver and swim around him with no fear. At times they just won’t leave you alone until you move away from them. They are found singly or in pairs and sometimes in small groups. They have been documented making use of acoustic behavior, using muscular movements to twist the body and deforming the swim bladder to produce sounds. The sounds are thought to be used to defend territory. A very approachable fish for photographers.
Longfin bannerfish are found on the East coast of Africa from south of Durban to the Red sea and eastwards to the mid Pacific . Juveniles are sometimes found close inshore in rock pools and they are found around jetties, in harbors and on offshore reefs to a depth of 75 meters. They are relatively common reef dwellers.
With their long pointed mouth and bristle like teeth which are suited for rooting in crevices , they feed on zoo-plankton and bottom dwelling invertebrates which include corals. They spend most of their time cruising the reef picking food off the bottom. Juveniles have been seen taking parasites off of other fish.
They have not yet been bred in captivity although people are trying. They are thought to spawn seasonally in pairs and the eggs larvae and fry are thought to drift with the current before swimming to the bottom. Some advanced aquarist’s are attempting to induce spawning in tanks with temperature changes. Some success has been achieved with a closely related species, the Schooling Bannerfish Heniochus diphreutes.
Because of their bright coloration these fish are kept in aquariums and are relatively hardy fish being much easier to keep than their close relatives the butterfly fish and their look alikes the Moorish Idol. They will readily accept most foods and are not that difficult to look after. They are suitable for intermediate level aquarists onward. Because of the size they grow to they need a relatively large tank with overhangs and caves to hide in. Tangs and other aggressive fish species may bully them. As they will eat corals they are not suitable for a reef tank. They are sociable fish and it is recommended that they be kept in threes so as to prevent one fish from becoming too dominant.
Allen, G.R., Steene, R. & M. Allen. 1998. A Guide to Angelfishes & Butterflyfishes. Odyssey Publishing/Tropical Reef Research. Pp. 250. –