Harlequin Rasbora (Trigonostigma heteromorpha)

Common Name:

Harlequin Rasbora.

Other Name:

Harlequin Fish.

Scientific Name:

Trigonostigma heteromorpha.

Family:

Cyprinidae.

Distribution:

Narathiwat, Thailand south to Sumatra, Indonesia.

Size:

Approx 1.5-2.0 inches.

Diet:

They feed on small invertebrates in the wild. They'll take small live foods and prepared foods in a tank setting.

Water Temperature:

73 to 82 degrees Fahrenheit (23-28 degrees Celsius).

Water Chemistry:

To breed, they must have slightly alkaline soft water. They may be acclimated to alkaline water or harder water. They are extremely susceptible to velvet, so their water needs to be kept very clean (and it may also mean that they are ill-suited for water that is out of their comfort zone).

pH:

6.0-7.5 (but they won't breed in alkaline water).

Life Span:

6 years.

Description:

These fish are rounded to two points (where the mouth and caudal peduncle are located). The caudal fin emanates from the caudal peduncle in a manner similar to that of the mammalian dolphin. The fins are tinged with red.

The body has a base color of silver and is coloured in a metallic red. There is a large spot posterior to the dorsal region and anterior to the caudal peduncle. This spot is black, triangular and prominent.

Behaviour:

These are peaceful schooling fish that will not bother any tank mates. Keep them in groups of six or more.

They feel most comfortable in vegetated tanks, but they also need room to swim, so a swimming arena should be provided within their tanks.

Sexing:

Males generally have thinner bodies than there female counterparts. There may be sexual dimorphism with regard to the triangular black region near the caudal peduncle.

Breeding:

They are a black water species in the wild and should be kept as such in order to breed them. They need warm, very soft water (possibly accentuated with black water extract). The tank should also be decorated with broad-leaved plants. It has been suggested that live foods may bring them into condition for breeding.

Males do a trembling display dance in the morning. They may also try to direct the females toward the leaves. Once she is ready, she will turn upside down and rub her ventral surface against the underside of the leaves. The male continues the dance, wraps himself around her and fertilizes the eggs, which float to the undersides of the leaves. 100+ eggs may be laid over the course of a couple of hours.

Breeders should then be removed from the tank, as they are obligate consumers of fry and their eggs.

The eggs will hatch within 24 hours. The fry will eat infusoria or newly hatched brine shrimp, but may do well on fry food formulated for egg layers.

Minimum recommended tank size:

10-15 gallons.

Tank levels:

Top-Mid.

Natural Conditions:

Forest streams, usually partially covered with vegetation.

Miscellaneous:

For a long time, this fish was known as Rasbora heteromorpha and appears as such in most literature and most pet shops.

There are also albino and black morphs available in the hobby. Unfortunately they are nowhere near as attractive as the wild type.

Photo Credit:

Photos 1-2 supplied courtesy and ^© Molino
Photo 3 supplied courtesy and ^©BrownEyes.
Photo 4 supplied courtesy and ^©Chapman76.
Photo 5 supplied courtesy and ^©Off-ice.