Red-tail black shark

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: sand.

Behavior

Plant interaction: plant safe.

Feeding

Omnivore that grazes on algae and biofilm but needs supplemental feeding. Sinking pellets, algae wafers, frozen bloodworm, frozen brine shrimp, blanched zucchini, blanched peas. Feeds on the bottom. Claims food that drops into its territory and defends it from other bottom-feeders. Feed once or twice daily.

Compatibility

• Territorial bottom-dweller, same behavioral profile as the rainbow shark but generally considered slightly more aggressive. One per tank, no exceptions. Two red-tail sharks will fight until one is dead or so stressed it stops eating.
• Don't keep with rainbow sharks, Chinese algae eaters, or any other bottom-dwelling fish with a similar body shape. These trigger the strongest territorial response.
• Tankmates should be robust mid-water or surface-dwelling species: barbs, larger tetras, rainbowfish, danios. The shark claims the bottom and occasionally chases interlopers but mostly leaves fish in other zones alone.
• Aggression escalates with age. A 5 cm juvenile in a community tank is mild-mannered. A 12 cm adult in the same tank is the undisputed ruler of the bottom half.

Origin and habitat

Epalzeorhynchos bicolor, the red-tailed black shark, is a striking cyprinid endemic to central and western Thailand, jet-black with a single vivid red or orange tail and, despite the name, no relation to true sharks; it is a sharkminnow in the carp family named for its tall dorsal fin and torpedo shape. Hugh Smith described it in 1931 as Labeo bicolor from a tributary of the Chao Phraya, and it was later moved to Epalzeorhynchos. Its wild story is dramatic: historic records come from the lower Chao Phraya, Mae Klong, and Bang Pakong systems, but dams, drained wetlands, deforestation, and agricultural pollution wiped it out, and it was thought extinct in the wild from 1996 until a small remnant population turned up in 2011. IUCN lists it as Critically Endangered. None of that touches the aquarium supply, though, since every red-tail shark in the trade is farm-bred in Southeast Asia, so its wild plight is a habitat problem rather than a collection one. It grows to around 12 to 15 cm. The look-alike rainbow shark, E. frenatum, is told apart by having red on all its fins, not just the tail.

Breeding

Red-tail sharks are not bred in home aquariums. Their intense intolerance of one another keeps a male and female from pairing peacefully in a tank, and the natural spawning triggers are not reproducible at home, so the trade depends entirely on commercial farms in Southeast Asia, where spawning is induced, most likely with hormones. Sexing is unreliable, and home spawnings practically never happen.

Common problems

Territorial aggression is the defining trait and it sharpens with age: a small juvenile is mild, but an adult claims the bottom of the tank and will fight another red-tail or a rainbow shark to the death, so the rule is one shark per tank with no exceptions. The fish is otherwise hardy, with ich on new arrivals the usual ailment, cleared by standard treatment. A red tail that fades toward pale orange is usually short on diet or stressed, and colour-enhancing food helps. The Critically Endangered status worries some keepers, but since all stock is captive-bred, buying one has no effect on the wild population. As with the rainbow shark, they jump when startled, so a tight lid is sensible.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size