About the Rainbow Shark
Species Type: Freshwater Fish
Care Level: Moderate. May tolerate only a narrow range of water parameters, have specific dietary requirements including frozen or even live foods, may have behaviors that severely limit potential tankmates or may require a specialized aquarium setup.
Origin: Thailand, Laos and Cambodia, in the Mekong, Chao Phraya, Xe Bangfai and Maeklong basins. Migratory; found in rivers and streams with sandy or rocky substrates, moving into seasonally flooded forest. Declining in parts of its range, possibly endangered. Most available fish will have been captive bred in SE Asia.
Compatibility/Temperament: Territorial and combative with its own species; best kept in solitude (as they seem to live in their habitat). Young fish tend to be secretive, but as they mature some can become aggressive, especially with their own or similar species. This "shark" will get along with some of the loaches (Botia sp.) but other bottom fish should be avoided. Upper fish such as the medium barbs, rasbora and danios would be suitable, especially in the suggested aquascape [see under Discussion]. In a large aquarium (6+ feet) a group of 6 could be attempted, but any fewer would likely result in the death of subordinate fish within the group.
Compared to its cousin, Epalzeorhynchos bicolor (Red Tail Shark), this species is more suitable for the home aquarium provided it has a spacious tank which should be no less than 4 feet in length. While it does eat algae, it is not proficient and should not be acquired solely for that purpose. However, one member reports that this fish will spend hours roaming around the tank looking for algae; in his experience the fish has become more peaceful as it aged and has become more nocturnal.
There is a variant form with yellowish rather than reddish fins. An albino form [pictured in the second photo above] is actually another species, Epalzeorhynchos munense (Smith, 1934), that is near identical to the present species in behaviour and requirements. The body colouration on the Rainbow Shark can be darker or lighter; a particularly colourful form was actually described as a distinct species, Labeo erythrura, by Fowler [who described the subject species] in 1937 but that turned out to be conspecific [same species] and the name is now an (invalid) synonym of the present species.
Males usually show a dark margin to the anal fin; otherwise, there is no discernible difference between sexes other than the rounder appearance of females. Probably not bred in aquaria; commercial breeding using hormones occurs in the far east to provide fish for the aquarium hobby.
This fish can live more than 15 years and deserves the proper environment. A suitable aquascape would be a river/stream environment with a gravel substrate with rock boulders and bogwood arranged to provide several hiding spots, and a reasonable flow lengthwise down the tank from the filter to replicate a stream current. Hardy plants such as Java Fern and Anubias can be attached to the rock and bogwood.
Originally described in 1934 by H.W. Fowler and placed in the genus Labeo [= "one who has large lips"] under the species name frenatus. The species epithet is sometimes seen spelled frenatum; frenatus is the recognized accepted spelling. In 1998 [Yang & Winterbottom] the species was moved to the present genus Epalzeorhynchos [erected by Bleeker, 1855] which contains five species, two of which are the red tailed shark (E. bicolor) and the Flying Fox (E. kalopterus).
Some ichthyologists consider this genus to be in the subfamily Labeoninae, others in Cyprininae; this is still disputed. There are three tribes (if in Labeoninae) or three subtribes under the tribe Labeonini (if in Cyprininae).
Yang, J.-X. and R. Winterbottom (1998), "Phylogeny and zoogeography of the cyprinid genus Epalzeorhynchos Bleeker (Cyprinidae: Ostariophysi)," Copeia (1), pp. 48-63.
Rainbow Shark Diet
Naturally feeds on algae, zooplankton and phytoplankton. Suitable aquarium foods are sinking pellets/tablets including those with vegetable (algae, spirulina) as well as fish/shrimp, frozen bloodworms, daphnia, artemia, and vegetable matter such as blanched spinach, shelled peas, chopped fruit.
Attains 6 inches.
Minimum Tank Suggestion
48 inches in length.
Ideal water parameters for Rainbow Shark
Soft to moderately hard (< 15 dGH), slightly acidic to slightly basic (pH 6.5 to 7.5) water, temperature 22-26C/72-78F. Intolerant of organic wastes (keep nitrates below 10ppm), and requires somewhat higher oxygen content which can be supplied with temperatures not exceeding the given range and adequate water movement from the filter.