Max Size: 5cm

Harlequin Rasbora (Trigonostigma heteromorpha)

Harlequin Rasboras are attractive, peaceful, lively and relatively hardy, making them suitable for a well-planted community aquarium with other small temperate fish or in a species only aquascaped nano aquarium.

Harlequin Rasboras are a shoaling fish that you should keep in groups of at least eight individuals. Maintaining these fish in more significant numbers will create a stunning display. You can keep Harlequin Rasboras with most fish, and they will not bother any other species.

Ideal tankmates for the Harlequin Rasboras could include small Tetras, Bettas, Dwarf Barbs, Dwarf Gouramis, smaller Danios, other Micro Rasboras, and Corydoras Catfish. However, You must not house these fish with larger and more aggressive species such as Cichlids and bigger Barbs as they will be seen as an easy snack.

The ideal aquarium setup for your Harlequin Rasboras would be well planted with soft, acidic water, mimicking their natural environment. It would also benefit your fish if you had a soft, dark sandy substrate with driftwood roots and branches placed so that plenty of shady spots and hiding places are formed.

Adding dried leaf litter would also be beneficial and would further accentuate the natural feel as it stains the water brown as they decay. Harlequin Rasboras prefers dim lighting, so adding floating plants to diffuse the light will also be appreciated. However, make sure you give these fish enough room to swim around.

Harlequin Rasboras have reddish copper, metallic affect bodies contrasted by a signature black triangular-shaped wedge that starts at their dorsal fin and continues to the base of their caudal fin. In addition, their fins tend to be lined with red. Captive bred' black' and 'gold' strains of Harlequin Rasboras are also occasionally available.


Harlequin Rasbora
Harlequin Rasbora
Longfin Harlequin Rasbora
Harlequin Rasbora
Harlequin Rasboras
Blue Harlequin Rasbora
Harlequin Rasboras
Harlequin Rasboras
Harlequin Rasboras
Harlequin Rasbora
Harlequin Rasbora
Harlequin Rasbora
Harlequin Rasbora
Quick Facts
Scientific NameTrigonostigma heteromorpha
Year Described1904
Other NamesRed Rasbora, Harlequin Fish, Red Razor
OriginsIndonesia, Malaysia, Singapore, Thailand
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 6+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH5.5 - 7.0
GH2 - 15
TDS18 - 215
72 - 80℉
22.2 - 26.7℃


In the home aquarium, the Harlequin Rasbora will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Sexual Dimorphism

It is pretty easy to determine the sex of a Harlequin Rasbora. The males are slimmer and usually have more distinctive colours than the females, and the triangular patch is rounder and more elongated in the male. In contrast, the females are plumper and typically duller than the males.

The Harlequin Rasbora has been featured on the following stamps

Singapore - 1962