Profile of the Red Rasbora (Harlequin Rasbora) fish breed

Harlequin rasbora fish with yellow and black scales swimming closeup

The harlequin rasbora is a favorite among fish hobbyists because it is simple to care for and has a stunning metallic color. A huge school of fish adds color and movement to an aquarium. This fish is ideal for a tiny community tank since it gets along well with most other species. Keep it with smaller fish of the same size since larger fish could be drawn to its sheen and try to eat it because it is a tiny fish.

Species Overview

Common Name: Red rasbora

Scientific Name: Trigonostigma heteromorpha

Adult Size: 1.75 inches (4.5 centimeters)

Life Expectancy: 6 years


Family Cyprinidae
Origin Southeast Asia, Malaysia, Singapore, Sumatra, Thailand
Social Peaceful, suitable for community tank
Top to mid-dwelling
10 gallon
Diet Omnivore
Breeding Egglayer
Care Intermediate
pH 6.0 to 7.5
Hardness Up to 12 dGH
73 to 82 F (23 to 28 C)

Origin and Distribution

The harlequin rasbora is a native of southern Thailand, Sumatra, Malaysia, and Singapore. It lives in streams and waters with low mineral content and large amounts of dissolved humic acids, which are typical of water that passes through drowned woods. These forests' wet soils prevent the complete decomposition of leaf litter, which leads to the production of peat and the leaching of humic acids. These environmental factors are similar to those in South American blackwater environments.

Colors and Markings

The harlequin rasbora is undoubtedly the most well-known of the more than fifty species of rasbora. The body is a reddish-copper hue and is frequently referred to as a red rasbora. A stunning black wedge covers the back half of the body. The distinctive triangular patch extends from the area close to the dorsal fin to a position close to the caudal fin. This species resembles Rasbora espei and R. hengeli in appearance.


As a schooling fish, the harlequin rasbora should be kept in groups of eight to ten. Even more numerous schools provide a stunning spectacle. Any fish may be kept with harlequins as long as it is not a huge, predatory fish. It doesn't bite or fight with other species. Cardinal tetras, bettas, neon tetras, tiny barbs, dwarf gouramis, danios, other small rasboras, and cory catfish are a few possible suitable tankmates.

Harlequin Rasbora Habitat and Care

Rasboras are exclusively found in freshwater and are not found in brackish waters. They favor Southeast Asian lowland waters because they are soft and acidic. Harlequins like environments with patches of thick foliage, a swimming hole that is open to the public, a dark substrate, and soft lighting.

Reside plants should be added to an aquarium where harlequin rasboras will live. Make space for swimming between clumps of vegetation like Cryptocoryne species, which are among the plants that naturally occupy the waters where the harlequin rasbora lives.

Harlequin Rasbora Diet and Feeding

All meals are accepted by harlequins, however they favor live foods whenever feasible. In the wild, insects make up the majority of their food. However, in addition to flake meals, they will also take frozen and freeze-dried foods. A diversified diet will prevent digestive issues or illness susceptibility from happening. When conditioning before breeding, brine shrimp, daphnia, and any kind of worm are great supplementary feeds.

Gender Differences

Male harlequins have a rounded extension at the bottom of the unique black wedge covering the fish's rear and are more slender than females. On females, the black wedge is completely straight. Additionally, the harlequin rasbora female is bigger than the male.

Breeding the Harlequin Rasbora

Harlequins are among the most challenging tropical freshwater species to spawn, however spawning is possible provided the right circumstances are created. Before attempting to spawn, choose young individuals and condition them with live feeds like daphnia and mosquito larvae. When it comes to reproducing, the harlequin rasbora is different from other well-known rasboras in the aquarium. Harlequin rasboras are egg layers as opposed to other rasboras, which spread their eggs.

Young harlequins can be bred in groups in a single tank. Keep two males for every female when they are generated in groups. To replicate the humic acid concentrations found in the fish's native waters, hobbyists who are determined to mimic natural conditions as closely as possible may choose to filter the aquarium water over peat. However, this is not necessary if the basic water chemistry parameters (no more than 4 dGH of hardness, pH of around 6.4) are correctly maintained. For spawning, water should be between 76 and 80 degrees Fahrenheit. Broad-leaved plants like Cryptocorynes or others should be added to the breeding tank.

After setting up the breeding tank, introduce the breeding animals in the late afternoon. Spawning often starts in the morning, with the male shaking and dancing in front of the female. This activity is used to guide the female toward a suitable plant where she will lay her eggs. The male may be seen moving the female to the spawning site by pushing her sides and rubbing his belly on her back.

The female will flip over and rub her belly on the underside of a leaf when she is ready to spawn, inviting the male to follow her. While still trembling, the male will approach her, wrap himself around her, and fertilize the eggs as they are released. At one moment, six to twelve eggs are deposited. The ovulated eggs rise and cling to the leaf undersides. Up to 300 eggs may be deposited in just one to two hours, while 80 to 100 are more normal.

Remove the breeding stock from the tank once spawning is finished since they will eat the fry once they hatch. The eggs will hatch in about 24 hours in water that is around 80 degrees Fahrenheit. The yolk sac is absorbed over the subsequent 12 to 24 hours that the transparent fry is still connected to the leaf where the eggs were placed.

After this procedure is finished, the fry become free-swimming and need extremely small-sized feeds like live infusoria for seven to fourteen days. Then, the fry can eat brine shrimp that have just hatched. Commercially prepared feeds for an egglayer can also be utilized if infusoria are not accessible. The young harlequin rasboras then mature sexually after six to nine months.

More Pet Fish Species and Further Research

If harlequin rasboras appeal to you, and you are interested in some compatible fish for your aquarium, read up on:

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