What tank size does a Harlequin Rasbora need?

A Harlequin Rasbora needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Harlequin Rasbora need?

Harlequin Rasbora does best at 22–28 °C (71.6–82.4 °F), pH 5–7.5 and a general hardness of 1–12 °dGH.

What group size does a Harlequin Rasbora need?

Harlequin Rasbora is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.

Is the Harlequin Rasbora suitable for beginners?

Yes — Harlequin Rasbora is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Species library

Harlequin Rasbora

Trigonostigma heteromorpha

Cyprinidae

FishDifficulty: ●●○○○Data: well-established

📷 NasserHalaweh · CC BY-SA 4.0 · resized · Wikimedia Commons

Harlequin Rasbora — Trigonostigma heteromorpha — 📷 NasserHalaweh · CC BY-SA 4.0 · resized · Wikimedia Commons

About

The harlequin rasbora is a hardy, peaceful cyprinid from the peat swamps and blackwater streams of the Malay Peninsula, Sumatra and Thailand. It is instantly recognised by the black wedge-shaped 'harlequin' patch on its coppery-pink flanks. Adaptable and long-lived, it is one of the best beginner shoaling fish, forming coordinated groups that move beautifully through planted community aquaria.

Care

Keep in shoals of 8+ in a planted tank with soft to moderately hard water and gentle flow. Very adaptable and peaceful, ideal for community setups.

Diet

Easygoing omnivore; feed a varied diet of dry foods plus frozen/live foods for best colour.

Tankmate compatibility

Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Full tank-mates guide with reasons →

Telling males from females

What works for this species, most reliable first.

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.

All the methods, with diagrams

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Frequently asked questions

What tank size does a Harlequin Rasbora need?: A Harlequin Rasbora needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Harlequin Rasbora need?: Harlequin Rasbora does best at 22–28 °C (71.6–82.4 °F), pH 5–7.5 and a general hardness of 1–12 °dGH.
What group size does a Harlequin Rasbora need?: Harlequin Rasbora is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.
Is the Harlequin Rasbora suitable for beginners?: Yes — Harlequin Rasbora is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Sources

Water & tank

Temperature22–28°C

Optimal temp.23–26°C

pH5–7.5

Hardness (GH)1–12°d

Carbonate (KH)0–8°d

Adult size4.5 cm

Min. volume≥ 60 L

Min. tank length≥ 60 cm

Group size≥ 8

Swimming zoneMid

TemperamentPeaceful

Water typeFreshwater

FlowLow

Lifespan~6 yrs

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