The schooling coachman is a white fish with two broad vertical black bars - one running across its pectoral fin to the front of its dorsal fin and the other from the tip of its ventral fin to just behind its dorsal fin. The coachman also has a small black bar extending up its forehead from its eye, and yellow pectoral and tail fins. It's most notable feature is the elongated fourth spine of its dorsal fin, leading into a long, white filament that extends far beyond the coachman's tail. The adult schooling coachman grows a short spine in front of each eye.
It is no coincidence that this coachman looks very similar to the Moorish idol - both are species of butterflyfish. Their resemblance is so uncanny, that the schooling coachman is commonly called the "poorman's Moorish idol". The Moorish idol is a highly desirable and common fish in home saltwater aquaria (there's even one in Finding Nemo) and the schooling coachman is often sold as a cheaper alternative in pet stores.
As the name suggests, the schooling coachman commonly lives in large schools. It is common in lagoons and along reef walls on the south-eastern African coast, the Red Sea and throughout the Indo-Pacific - even as far as Japan, Hawaii and New Zealand. Although it is found in tropical areas, it tends to prefer deep, cool waters and areas of cold-water upwelling.
The schooling coachman is a carnivore, feeding on tiny organisms, particularly zooplankton and has a set of very fine, hair-like teeth (a feature common in butterflyfishes) that enable it to consume organisms that are so small that they are usually passed through the gills of other fish.
The juvenile schooling coachman acts as a cleaner fish, picking parasites and bits of dead tissue off of larger fish species and this behaviour is also seen in some populations of adults where suitable client fish are present in abundance.
What is a butterflyfish?
Butterflyfish belong to a family called Chaetodontidae, meaning “hair tooth”. The name “butterflyfish" is a reference to the dark eyespots that many butterflyfishes have on their flanks to dissuade predators, a survival strategy employed by many species of actual butterfly.
Southern African coral reefs are home to more than 20 species of these colourful, flattened fish. Globally there are 129 known species of butterflyfish.
Butterflyfish are usually diurnal, actively hunting during the day and taking shelter during the night.
You may have noticed that butterflyfish and angelfish look similar, however butterflyfish are generally smaller and lack the spiny armoured plates on their gill covers.
Fish that carry the name of "bannerfish" or "coralfish" are often also in the butterflyfish family.