Rainbow Shark
Epalzeorhynchos frenatum
Cyprinidae
About
The rainbow shark is not a shark but a labeonine cyprinid from the Mekong, Chao Phraya and Xe Bangfai basins, sold at 4-5 cm and reaching about 15 cm. What grows fastest is not the fish but its temper: adults claim a cave or rock pile and, according to Seriously Fish, defend a territory at least a metre across, evicting anything that shares the bottom and reserving real violence for similar-looking species. In all but exceptional tanks it is a one-specimen fish, and that includes the albino form often sold as the calmer variety, which is the same species under a different colour.
Care
Keep a single specimen in at least 200 L with a 120 cm footprint, sandy substrate, caves and enough hardscape to break the line of sight. Pick fast upper- and mid-water tankmates, leave the floor to the shark, and fit a tight lid because it jumps.
Diet
Grazes algae and biofilm; base the diet on vegetable-rich dried foods, spirulina wafers and blanched vegetables, with small live or frozen foods a few times a week.
Tankmate compatibility
Gets along with (42)
Possible with care (184)
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 Rainbow Shark need?
- A Rainbow 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 Rainbow Shark need?
- Rainbow Shark does best at 20–27 °C (68–80.6 °F), pH 6.5–8 and a general hardness of 2–15 °dGH.
- Is the Rainbow Shark suitable for beginners?
- Rainbow 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.