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Lambchop Rasbora (Espei Rasbora)

Trigonostigma espei

The *Trigonostigma espei*, delicately called "Espei Rasbora" or popularly in England "Lambchop Rasbora" (due to its mark), is the evolutionary jewel for compact aquariums that outclasses the Harlequin in pure chromatic saturation. Although visually similar to the more famous and stubby Harlequin, the Espei is significantly smaller (just 3 centimeters / 1.2 inches), boasts a leaner, narrower and more hydrodynamic silhouette, but above all explodes in a coloring of a fiery orange or incandescent bronze red that monopolizes the sight. The black mark on the body is thinner, curved and streamlined, precisely recalling the silhouette of a meat chop (lambchop). More compact, more shy but incomparably more flashy, the Espei is the luxury and preferred inhabitant for tanks dedicated to the pure, impeccable and meticulous oriental 'Aquascaping'.

Taxonomy
Class:Actinopteri
Order:Cypriniformes
Family:Cyprinidae
Subfamily:Rasborinae
Genus:Trigonostigma
Species:Trigonostigma espei*
* Spesso confusa nei negozi con la simile Trigonostigma hengeli

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Water Temperature

23 - 28 °C

pH Value

5.5 - 7

Water type

Freshwater

Tank level

Middle

Adult size

3 cm

Minimum tank volume

>= 50 L

Minimum group

>= 10

GH

1 - 12 dGH

KH

1 - 6 dKH

TDS

25 - 240 ppm

Conductivity

39 - 375 uS/cm

Species description

Geographical Origin and Habitat: Endemic to southwestern Thailand (Krabi, Surat Thani provinces) and some swamps in Cambodia. Exclusively inhabits flooded forests and very slow-flowing (or stagnant) peat pools protected by dense reeds. The water is saturated with tannins, taking on the typical color of dark tea (blackwater).
Taxonomy and Morphology: Minute Cyprinid (not a characin) commonly known as Espei Rasbora or "Lambchop Rasbora". Barely reaches 3 cm (1.2 inches). It is very often confused with its congener T. heteromorpha, but is easily distinguished by its much more slender body and the black spot which has the shape of a thinner "lamb chop," rather than a vast dark triangle.
Social Behavior: An animal of proverbial shyness but lovely nature. Forms tight and sinuous schools. To instill confidence and make them show their brightest hues, the school must never be less than 10-12 specimens; in smaller numbers they remain stressed and faded, hidden among the foliage.
Coloration and Sexual Dimorphism: Wonderful coppery-bronze or bright orange coloration that becomes fiery in courting males. The posterior flank is marked by the typical inverted "L" (lambchop) black spot. Females are slightly less colorful but have a distinctly rounder abdomen.

Care, breeding and tankmates

Aquarium Setup: Dark and peaceful tank of minimum 60 cm (24 inches). Amber sandy bottom, dense fine-leaved vegetation, bog roots, and an abundant layer of dried leaves on the bottom (Catappa, Oak) and alder cones to simulate blackwater. Filtered light and almost absent water current are imperative.
Diet and Feeding: Micropredator. The tiny esophagus prevents ingestion of standard food sizes. Feed with crushed excellent quality micro-pellets or powders. The chromatic peak is achieved by offering tiny live and frozen food: newly hatched brine shrimp, copepods (Cyclops), and micro-daphnia.
Water Quality: Sensitive to dissolved salts and nitrates. Requires distinctly acidic and soft waters: pH between 5.5 and 7.0 (never alkaline) and GH from 1.0 to 12.0. Stable tropical temperature between 23.0 and 28.0 °C (73-82 °F). Small but regular water changes (RO water with specific blackwater salts) prevent immune drops.
Compatibility and Cohabitation: The ideal tankmate for aquariums with Betta splendens, Honey Gouramis, micro-rasboras (Boraras), and Kuhli Loaches. Due to its small size, it should never be paired with large predatory fish like Angelfish or Cichlids that would swallow it without hesitation.
Aquarium Breeding: Peculiar and fascinating. Unlike many cyprinids that scatter eggs, this species swims upside down and glues about ten eggs at a time (around 60 in total) to the underside of a broad leaf (e.g. Cryptocoryne or Java Fern). In a community tank, eggs and fry have no chance of surviving parental mouths.
Risks and Diseases: They collapse instantly (Velvet disease, fin rot) in the presence of ammonia or if placed in new, uncycled tanks. Bright light, light-colored backgrounds, or lack of hiding places cause fatal shock from chronic stress.

Geographic Origin and Distribution

Endemic to southwestern Thailand (Krabi, Surat Thani provinces) and some swamps in Cambodia. Exclusively inhabits flooded forests and very slow-flowing (or stagnant) peat pools protected by dense reeds. The water is saturated with tannins, taking on the typical color of dark tea (blackwater).

Origin

Selective breeding and cultivarsNorth AmericaSouth and Southeast Asia

Fish profile

Temperament
Peaceful
They are peaceful and somewhat timid if kept in numbers that are too small. A school of at least eight to ten individuals brings out their best behavior. In a properly sized group, they exhibit fascinating social dynamics and vibrant colors.
Diet
Omnivore
They are micropredators that feed on tiny insects in nature. In the aquarium, they readily accept high-quality micro-pellets and crushed flakes. Supplementing their diet with live or frozen daphnia and cyclops ensures optimal health and coloration.
Sex ratio
School
A mixed group works well, though more females can reduce male competition. Males are generally slimmer and more intensely colored during the breeding season. Having a large enough school ensures any minor aggression is spread out evenly.
Feeding frequency
Twice daily
It is best to feed them small amounts two or three times daily. Their small stomachs require frequent but tiny meals to prevent bloating. Removing uneaten food after a few minutes helps maintain excellent water quality.
Bioload
Low
This species produces very little bioload due to its small size. Weekly water changes and standard filtration are adequate to keep parameters pristine. Still, their schooling nature means the total bioload of the group must be considered.
Flow
Weak
They come from slow-moving rivers and shaded forest streams. Gentle to moderate water circulation mimics their natural environment perfectly. Strong flow from oversized pumps can easily exhaust these delicate swimmers.
Jump risk
No
Reproduction
Oviparous
Breeding is a challenging but rewarding endeavor for advanced hobbyists. They are egg-scatterers that lay adhesive eggs on the undersides of broad leaves. The parents provide no care and should be removed after spawning to prevent egg cannibalism.
Compatibility & tankmates
Peaceful
They are exceptionally peaceful and make great community fish. They should never be kept with large or aggressive tank mates that might eat them. Ideal companions include small tetras, peaceful bottom dwellers, and dwarf shrimp.
Tank level
Middle
They predominantly occupy the middle to upper levels of the water column. They enjoy open swimming spaces surrounded by tall aquatic plants. Rarely do they venture to the substrate unless chasing a sinking morsel of food.

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level
3.1 ± 0.4 se
Resilience
High (less than 15 months)
Phylogenetic uniqueness (PD50)
0.5312
Bayesian Length-Weight
a = 0.00891, b = 3.02
VulnerabilityLow vulnerability (10 / 100)

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

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Last updated: 06/30/2026
Lambchop Rasbora (Espei Rasbora) (Trigonostigma espei) Care Guide & Tank Setup | Atlarium