Taxonomy & naming
Bleeker described the species in 1850, with the type locality at Banjarmasin in southern Borneo. The valid name is Epalzeorhynchos kalopterum, with the neuter ending used by the Catalog of Fishes; the older spelling kalopterus is still seen in the hobby and in the store listings. It is frequently confused with Crossocheilus species sold as Siamese algae eaters, which lack the second barbel pair and the bold black and gold stripes of the flying fox.
Morphology
A slender, torpedo-shaped fish with a ventral sucker-like mouth and two pairs of barbels. A black stripe runs from the snout through the eye to the tail base, with a gold stripe above it, and the fins have dark and yellow-orange markings. Maximum length is given as 6.5 in TL according to FishBase.
Habitat
It occurs in Borneo, Sumatra, Java and the lower Malay Peninsula, in clear, flowing streams and rivers over rock and gravel, in shaded water. FishBase gives a temperature range of 75–79 °F, pH 6.5 to 7.0 and hardness of 5 to 8 dH, and lists it as a demersal freshwater fish. It is often collected from under floating objects such as boats and floating houses.
Feeding
It grazes algae and biofilm from rocks and wood and takes small invertebrates. FishBase also lists worms, crustaceans, insects and plant matter in the diet. In aquaria it accepts algae wafers, flake and frozen foods, and grazes brush algae when young.
Mating
Wild mating behaviour has not been well described. Males are territorial towards their own kind and similar fish, and aggression between flying foxes is common.
Breeding
Spawning in home aquaria is rare. Trade fish are produced on farms using hormone induction, as with related Epalzeorhynchos, and wild stock is also exported.
In the aquarium
It is hardy in a tank with flow, hiding places and a tight lid. FishBase describes it as a solitary species with territorial adults and suggests a tank of at least 39.5 in. Adults chase each other and similar bottom fish, so it is best kept singly or in a large group in a big tank. It is peaceful with fish in other zones, and aggression rises with age.
Conservation
The IUCN Red List category is Least Concern, assessed in 2019. Habitat loss and collection for the aquarium trade could add pressure, but no population trend is documented here.