The Espe’s Rasbora is an adorable little cyprinid originating from overgrown jungle streams!

The Espe’s Rasbora Trigonostigma espei (previously Rasbora espei) is yet another amazing aquarium fish from Southeast Asia. It is a relative newcomer, described by Meinken as recently as 1967. This fish is found throughout the eastern slopes of the Gulf of Thailand in Cambodia and Thailand, and more recently, a population has been found on the Island Phu Quoc of Vietnam.

This small, agile cyprinid fish only reaches about an inch (3 cm) in length. It has unique bronze color with a pink blush, which you really won’t find on any other aquarium fish. Its color can vary a bit depending on the locality it comes from, with some specimens having a more intense red. Its most distinguishing feature is a black lambchop-shaped marking on the side. Hence, it is also popularly known as the Lambchop Rasbora, along with some other descriptive common names including False Harlequin, Narrow Wedge Harlequin, and Slim Harlequin.

This fish is often confused with two of its close relatives, the Harlequin RasboraTrigonostigma heteromorpha and the Glowlight RasboraTrigonostigma hengeli. The name ‘Espe’s Rasbora’ is also often mis-applied to the Hengel’s Rasbora, and both fish are frequently sold under the name of ‘False Harlequin’ as well.

Espe’s Rasbora can be distinquished from its conspecifics through close attention to some subtle differences. The Harlequin Rasbora is pale pink to bright red and is much stocker than its cousins. The Harlequin’s black mark is also much closer to a triangle shape and will have a noticeably blue tint. The Glowlight Rasbora is more of a butter-colored fish and will have an iridescent orange stripe above a thin and very rounded black triangle. The Espe’s Rasbora should be bronze pink in color and have no orange stripe above the black triangle.

Espe’s Rasbora is an agreeable little fish. It really couldn’t be friendlier and makes a great addition to any peaceful tank. They need to be kept in a groups of at least 8 to 10 individuals. Even though they tend not to swim in a tight school, the companionship of their own species is absolutely essential. A school could be housed in a 10-gallon tank as the bare minimum, but a 20-gallon aquarium will suit them best.

These very tolerant fish require little extra care, so they are a great fish for a beginning aquarist. To bring out their best colors, use a darker substrate and provide them with plenty of plants. The tank should be carefully covered as these fish are liable to jump if startled or excited. There simply isn’t a better fish to compliment a thoughtfully planted aquascape.

Scientific Classification


Espe’s Rasbora – Quick Aquarium Care

Aquarist Experience Level:Beginner
Aquarium Hardiness:Very hardy
Minimum Tank Size:10 gal (38 L)
Size of fish – inches1.2 inches (3.00 cm)
Temperature:73.0 to 80.0° F (22.8 to 26.7&deg C)

Habitat: Distribution / Background

The Espe’s Rasbora Trigonostigma espei (previously Rasbora espei) was described by Meinken in 1967. It is found in Southeast Asia throughout the eastern slopes of the Gulf of Thailand in the countries of Cambodia and Thailand, and a recent population was also found on the Island Phu Quoc of Vietnam.

This species is listed on the IUCN Red List as Least Concern (LC). Although trade has some impact on the populations, it is considered stable. Other common names it is known by include Lambchop Rabora, False Harlequin, Narrow Wedge Harlequin, Slim Harlequin, Rasbora Espei, and Espei Rasbora.

There are currently four distinct members in the Trigonostigma genus. These fish were previously contained in the Rasbora genus but were reclassified in 1999 by Kottelat and Witte. They were distinguished by their triangular pattern and coloring, as well as their reproductive method of depositing adhesive eggs underneath leaves or other matter rather than simply scattering them.

In nature, this rasbora inhabits thickly vegetated streams, ponds, pools, marshes, and swamps where the waters are calm or gently flowing. Due to the dense plant matter, tannins and other chemicals from decomposing organic debris sometimes stain the water a yellowish brown. The water is also soft and weakly acidic or neutral, and the forest canopies often keep it heavily shaded. These fish swim in schools and are known as micropredators, feeding on small insects, worms, crustaceans, and zooplankton.

  • Scientific Name: Trigonostigma espei
  • Social Grouping: Groups
  • IUCN Red List: LC – Least Concern


The Espe’s Rasbora is a small slender fish, reaching a total length of just over 1 inch (3 cm). They have a typical lifespan of 3 to 5 years with good care. Their primary color is copper-orange with a pinkish blush, and the body color appears to be increasingly reflective approaching the lateral line. It has a black lambchop-shaped marking on the side, and the fins are clear except for yellow triangles on the dorsal fin and tail. Depending on point of origin, some specimens are a more intense red.

  • Size of fish – inches: 1.2 inches (3.00 cm)
  • Lifespan: 3 years – They have an average lifespan of about 3 to 5 years with proper care.

Fish Keeping Difficulty

The Espe’s Rasbora is very hardy and makes a great fish for beginners. They are usually not very picky eaters and will thrive on quality flake foods. With well-filtered water and regular maintenance, these fish will do very well, but they must be kept in a school.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

The Espe’s Rasboras are omnivorous. In the wild, they feed on small insects, worms, crustaceans, and zooplankton. In the aquarium, their diet should be based around a quality flake or pellet food supplemented by the occasional live snack of brine shrimp or bloodworms. They will also welcome some blanched lettuce or spinach. These fish will do best when fed several times a day, but only offer what they can eat in 3 minutes or less at each feeding. If you feed only once per day, provide what they can eat in about 5 minutes.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day – Offer only what they can consume in 3 minutes or less with multiple feedings per day.

Aquarium Care

These fish are not exceptionally difficult to care for provided their water is kept clean. At least 25 to 50% of the tank water should be replaced once a month. If the tank is densely stocked, replace 20 to 25% weekly or every other week. The substrate should also be vacuumed during water changes to avoid accumulation of waste.

  • Water Changes: Monthly – If the tank is densely stocked, water changes should be done every other week.

Aquarium Setup

The Espe’s Rasbora is a hardy schooling species that will spend much of its time in the middle and upper regions of the aquarium. The tank should be no less than 18 inches (45 cm) long to allow these fish to comfortably school and swim back and forth. A school can be kept in a smaller, 10-gallon aquarium, but will do best in about a 20-gallon size. This rasbora’s colors can be quite stunning and will show best in soft, slightly acidic water conditions. Provide a good filter, but as these fish come from very sluggish waters, strong filtration is not necessary. The tank should be carefully covered as these fish are liable to jump if startled or excited.

A heavily planted tank will make them feel much more at home. A good aquascape would be dense plantings reaching the surface of the aquarium around the sides and back with a few broad-leaved plants for shelter. A dark substrate and areas of shadow will bring out this fish’s redder hues. Adding floating plants will give the fish extra security and help to diffuse the light entering the tank. Bogwood is also a great addition, as the tannins help maintain water parameters more closely resembling their natural environment. To create a natural feel and encourage the growth of microbe colonies, add dried leaves to the tank. The microbe colonies will also act as a secondary food source.

  • Minimum Tank Size: 10 gal (38 L) – Though a school can be kept in a smaller aquarium, they will do best in about a 20-gallon tank.
  • Suitable for Nano Tank: Yes
  • Substrate Type: Any
  • Lighting Needs: Moderate – normal lighting
  • Temperature: 73.0 to 80.0° F (22.8 to 26.7&deg C)
  • Breeding Temperature: 77.0° F – Breeding temperatures between 77 and 80° F (25 – 28° C).
  • Range ph: 6.0-8.0
  • Hardness Range: 1 – 15 dGH
  • Brackish: No
  • Water Movement: Moderate
  • Water Region: All – Espe’s Rasboras spend much of their time in the middle and upper region of the aquarium.

Social Behaviors

These fish must absolutely be kept in groups of at least 8 or more individuals. These rasboras are schooling fish by nature, but don’t always swim in a tight school unless the school is very large or there are other large fish in the tank. Regardless, these fish need to be kept in a group for their well-being. They may chase each other in their loose school, but injuries almost never result. Males will display their best colors as they compete for the attention of females.

These are generally peaceful fish with a disposition suited to the community aquarium; however, they are very active and may disturb the peace of less tolerant fish.

They can be kept with many popular community fish including other cyprinids as well as some of the characins, like tetras, and livebearers such as mollies, guppies, platies, and swordtail fish. They also do well with bottom-dwelling peaceful catfish, loaches, and even some of the dwarf cichlids. However, they will suffer in the company of overly large and aggressive fish.

  • Temperament: Peaceful – These peaceful fish will get nervous around larger tankmates.
  • Compatible with:
    • Same species – conspecifics: Yes – This fish is only comfortable kept with a school of its own kind. They need to be in groups of at least 8 to 10 individuals.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Threat – Because of their small size, aggressive fish are a threat.
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Safe
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Safe

Sexual differences

The mature males are thinner and more brightly colored than the females. Females will have a higher body and fuller belly. The dark, wedge-like markings on the males may also have a sharper, more definitive outline.

Breeding / Reproduction

Espe’s Rasboras are moderately difficult to breed, though if kept in a well-maintained aquarium with dense planting, you may see some young fish showing up. Although, like the other cyprinids, they exhibit no parental care for the young, they differ slightly in their spawning method. Unlike the open water egg scatterers, this rasbora attaches its eggs to the undersides of broad-leaved plants or other objects. In a controlled spawning, 1 or 2 pairs need be well-conditioned with small offerings of live foods several times a day, usually for about 4 weeks. This conditioning will also bring out the male’s color. When well fed, mature females should begin filling out with eggs.

Provide a dimly lit breeding tank and keep the water level low, at about 6 to 8″ (15 – 20 cm). The water should be very soft at about 2° dGH, slightly acidic with a pH of 5.3 to 5.7, and a temperature between 77 and 82.4° F (25 – 28° C). Filtration isn’t really necessary, but you can add a small air-powered sponge filter or some peat filtration. They need either artificial or live broad-leaved plants, like Microsorium or Cryptocoryne, for the eggs to adhere too. A spawning mop can also be added so any eggs that don’t attach to the leaves have a place to fall that’s out of the reach of the parents.

Place one or two pairs in the breeding tank, and spawning will usually occur in the morning hours. The male will direct the female to his selected location, almost always the underside of a broad-leaved plant. The male performs a courtship dance, and the spawn takes place under the plant leaves, with the partners swimming upside down. After the spawn, remove the parents as they will eat the eggs and darken the tank. At this time, lower the water level down to between 4 and 6 inches (10-15 cm), making sure the eggs are below the surface.

The fry will hatch in about 24 hours and be free-swimming in about 7 to 14 days. Feed the free swimming fry starter foods like infusoria for the first few days until they are large enough to eat baby brine shrimp. See Fish Food for Fry for information about types of foods for raising the young.

  • Ease of Breeding: Moderate

Fish Diseases

Espe’s Rasboras are very hardy, and disease is not usually a problem in a well-maintained aquarium. If good water quality, nutrition, and maintenance is not provided, some diseases that are common in rasboras are dropsy, fin rot, and Ich. Remember that any additions to a tank, such as new fish, plants, substrates, and decorations, can introduce disease. Properly clean or quarantine any additions to an established tank so as not to upset the balance.

These fish are very resilient, but knowing the signs of illness and catching and treating them early makes a huge difference. An outbreak of disease can often be limited to just one or a few fishes if dealt with at an early stage. The best way to proactively prevent disease is to give your fish the proper environment and a well-balanced diet. The more closely their environment resembles their natural habitat, the less stress the fish will have, making them healthier and happier. A stressed fish is more likely to acquire disease. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


Espe’s Rasboras are also sold as False Harlequins or Lambchop Rasboras. They are fairy inexpensive but somewhat difficult to find.  A select few fish stores will carry them, and they may be available online.



Featured Image Credit: Geza Farkas, Shutterstock