Red-Tail Shark
Epalzeorhynchos bicolor
Cyprinidae
About
The red-tail shark is a velvet-black cyprinid with a blood-red tail, endemic to Thailand and declared extinct in the wild in 1996 before small relict populations turned up again in the Chao Phraya basin in 2011 and the Mae Klong in 2014. Every fish in the trade is commercially produced, probably hormone-induced. It reaches around 13 cm and converts most of that growth into territorial aggression: Seriously Fish calls it highly unsuitable for the general community aquarium and recommends keeping it singly in the majority of cases. Two in one tank normally ends with one dead fish.
Care
One per tank, in 200 L or more with a 120 cm footprint, sand, caves and dense hardscape. Avoid other bottom-dwellers and any similarly shaped cyprinid entirely; slow, long-finned fish will be nipped. Keep the lid tight, as it jumps when it chases.
Diet
An algae and biofilm grazer rather than an algae-control fish. Feed vegetable-based dried foods and blanched vegetables with regular small frozen or live foods.
Tankmate compatibility
Gets along with (68)
Possible with care (158)
Avoid (45)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Colour and patternA hint only · from about 6 months, and only on a settled fish
In rainbowfish, killifish and several barbs the male carries the colour — deeper and more saturated, intensifying further when he displays.
- Extended finsA hint only · from about 8 months, and later in a suppressed male
On many cichlids and killifish the male's dorsal and anal fins draw out into trailing points as he matures, while the female's stay rounded.
- Belly depthA hint only · only on well-fed adults, and only as a comparison
For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.
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Frequently asked questions
- What tank size does a Red-Tail Shark need?
- A Red-Tail Shark needs an aquarium of at least 200 litres (52.8 US gallons) with a footprint at least 120 cm (47.2 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Red-Tail Shark need?
- Red-Tail Shark does best at 20–26 °C (68–78.8 °F), pH 6–8 and a general hardness of 2–15 °dGH.
- Is the Red-Tail Shark suitable for beginners?
- Red-Tail Shark sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.