The red-tailed black shark, Epalzeorhynchos bicolor, is a small freshwater fish in the carp group. Despite the common name it is not a true shark; the name refers to its streamlined profile and prominent dorsal fin. Taxonomically it is placed in the carp family, Cyprinidae, and is treated in regional fish accounts and aquarium literature (Cyprinidae resources). The informal "shark" label appears repeatedly in hobby and popular sources (name notes).

Identification

Adults show a deep, nearly uniform black body with a vividly colored red or orange tail fin. The contrast between body and tail is the species' most distinctive feature and the reason it is prized by aquarists. Juveniles may be less intensely colored. Sexual differences are subtle; males and females are similar in shape and color, so behavior and body shape during the breeding season are more informative than coloration alone.

Distribution and habitat

The species is native to a limited area of Southeast Asia and is generally considered endemic to parts of Thailand. In the wild it inhabits lowland streams, canals and vegetated waterways with moderate flow, soft substrate and areas of cover. Habitat alteration and water quality deterioration have reduced available habitat in many locations.

Behavior and diet

In nature the red-tailed black shark is omnivorous, grazing on algae and plant material while also taking small invertebrates. In captivity it accepts a range of prepared foods, along with live or frozen items that provide protein and vegetable matter. Individuals can be territorial, especially toward other similar-shaped fish, and may establish and defend a preferred area of the aquarium (diet and feeding).

Aquarium care

Its dramatic coloration makes it a popular aquarium species (aquarium resources). Recommended husbandry emphasizes stable water quality, moderate water flow, shaded areas and hiding places created by plants, driftwood or rockwork. Because of territorial tendencies, many keepers house a single specimen or maintain them with robust, non-shark-like tankmates. Captive-bred stocks are widely available and generally better suited to aquarium life than any remaining wild-caught individuals.

Conservation and trade

Although commonly kept in aquaria worldwide, the red-tailed black shark illustrates a conservation paradox: it can be abundant in trade while rare or threatened in its native range. Loss of habitat, pollution and collection pressure historically contributed to declines. Most aquarium specimens today are bred in captivity, which can reduce pressure on wild populations when captive-bred fish are chosen by hobbyists. Responsible practices include preferring captive-bred fish, avoiding release of aquarium specimens into the wild, and supporting habitat protection efforts in the species' native range.

  • Identification: black body with red tail.
  • Habitat: shallow streams, vegetated waterways.
  • Diet: omnivorous; accepts varied prepared and natural foods.
  • Trade: largely captive-bred; wild populations much reduced.

Further information and species accounts can be found in ichthyological guides and aquarium care references: carp family overview, Cyprinidae resources, common name notes, endemic species guides, regional faunas, aquarium resources, and diet and feeding.