Harlequin Rasboras: Characteristics, types, habitat care and more….

Harlequin rasboras or Trigonostigma heteromorpha  in scientific terms, are active and peaceful shoal fish, very suitable for community aquariums.


They are fish originating in southeast Asia and we find it in Malaysia, Singapore, Sumatra, Thailand.


Phylum : Chordata  Class: Actinopterygii  Order: Cypriniformes Family: Cyprinidae  Genus: Trigonostigma Species: T. Heteromorpha

Main Characteristics

The Harlequin rasbora’s  life expectancy oscillates between five and six years of age. As for the physical aspect, it is possible to find individuals whose shades vary between pale pink and red, as well as others with orange copper ones both on the upper and lower areas.

The Harlequin Fish is characterized by having a triangular mark on the back of one of its sides, which combines the blue color with beautiful purple reflections in front of the patch.

Depending on the colors, the following varieties of harlequin fish have been determined: Harlequin Rasbora (abundant golden color), Black Harlequin Rasbora (black Body and patch) and Blue Harlequin Rasbora (abundant blue). we invite you to read our article the anatomy of fish to lear more about such a topic

Harlequin rasboras: Blue Harlequin Rasbora

Harlequin Rasboras’ Habitat

Harlequin rasboras tend to live in shallow streams and rivers where Cryptocoryne prevails, which is their aquatic plant par excellence to feed. In this way, it is considered that the natural habitat of the harlequin fish is one that is characterized by environments with chemical substances such as tannins, which give a yellowish brown appearance to the water. The illumination of these sites is usually tenuous, with a level of acidity that varies between acid and neutral.

Harlequin Fish in Aquariums

To decorate the aquariums where you host the Harlequin rasboras is necessary to keep in mind that he will be better in those waters with dark substrate since in such environments his coloration highlights more. On the other hand, the aquarium can be made-up taking into account a soft, sandy substrate, with roots and branches of wood. The latter should be dispersed so that they may generate shadows and small caves where they can hide.


Water Conditions

The water temperature for the pond where a harlequin fish lives must be between 21 and 28 °c; The pH of the fish tank should vary between 5.0 and 7.5, while the hardness must present levels of 18 to 215 ppm.


Harlequin rasboras are micropredators , so they feed on small insects, crustaceans, worms and zooplankton. When they live in captivity they must be fed irregularly with live foods such as Daphnia, Artemia and Earthworm, adding also granules and flakes.

Behavior and compatibility with Other fish

Harlequin rasboras are recommended for all those ponds that are in good condition. Their peaceful behavior makes it easy for them to coexist with other fish, being just perfect for those who start in the Acuariofilia.

They  ease to adapt   to any type of water, makes it easy for them to live with diverse species such as tetras, cichlids dwarfs, catfish, viviparous, and Lochas. However, it is necessary to take into account their small size to prevent bigger species to attack them, and in this sense a number of companions of up to 10 are suggested.

Harlequin Rasboras’ Reproduction

The eggs of this species aren’t usually placed in a small thread on the surface, but on the back of the leaves of the aquatic plants. To ensure that juvenile specimens reach adulthood, it is advisable to give little light to the base of the pond, which must be covered with a mesh so that the eggs that fall off the leaves pass through it and the other fish do not eat them.  The pH for breeding fingerlings should be maintained between 5.0 and 6.0.

On the other hand, an air-operated sponge filter is recommended.  in a rare way, in this species the older individuals are the ones that perform the spawning, being less fertile the young specimens.  On the other hand, the time to change the future parents for a breeding pond is when the female is warned full of eggs and the males exhibit their best colors.

Females usually spawn, preferably in the morning and after a long courtship of the male, which includes drills in the possible regions where spawning will occur.

Then the female will put the eggs in small lots that will be fertilized before they put the other. It is known that it is the female who chooses the part of the leaf where the eggs will be placed. During that process it is not necessary to feed the adult fish. The eggs Hatching occurs, generally between 24 and 28 days.

let’s watch them


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