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Care guide · Freshwater · fish

Lambchop rasbora

Trigonostigma espei

Lambchop rasbora (Trigonostigma espei)
Photo: AverageWalrus · Source · CC BY-SA 4.0Resized and compressed; no cropping or colour changes.

The lambchop rasbora (Trigonostigma espei) combines a copper-orange body with a black marking that narrows towards the tail from the belly region. A larger group is particularly attractive in a planted aquarium: the fish seek each other's company but also explore sheltered margins individually. This small species suits a quiet community and is easily confused with other harlequin-like rasboras. Check the scientific name, adult markings and, where possible, origin before assembling a shoal. A few individuals among larger fish cannot replace a group of their own species. Plan the aquarium around roughly ten or more companions, providing shade as well as an open swimming lane.

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At a glance

Temperature
24–28 °C
pH
6.0–6.5
GH
1–10 °dGH
Aquarium length
At least 60 cm
Adult size
Approximately 3–3.5 cm
Group size
At least 10 individuals
Temperament
Peaceful

About this species

FishBase currently places Trigonostigma espei in Danionidae. Older sources use the broader family Cyprinidae. Trade names include Espe's rasbora and Rasbora espei. It is a distinct species, not an orange variety of the larger harlequin rasbora. In adult espei, the front of the body is also clearly orange. The related T. hengeli generally remains much paler there, with orange concentrated in a highlight above the dark marking.

Adult aquarium fish are described as approximately 3–3.5 cm in total length. This differs from standard length, excluding the tail fin, used by scientific databases. Very young fish can be difficult to distinguish; a shop label alone does not resolve their identity. Mature females are generally fuller, while males often show stronger colour. Colour intensity also varies with condition and lighting. Do not select a breeding pair solely from one bright photograph or a rounded belly after feeding.

Natural habitat

The species is known from Thailand and Cambodia; specialist sources also report records from Vietnam. Vegetated quiet waters and sheltered sections of small waterways are among the habitats described. Not every population occupies identical water: alongside soft, acidic conditions, limestone sites with nearly neutral to slightly alkaline water have been recorded. Southeast Asian origin alone therefore does not make an extreme blackwater aquarium compulsory.

Use the habitat structure as your main inspiration: plants around the margins, patches of shade and a clear route for the shoal. An uninterrupted canopy without swimming passages is no more useful than a completely bare tank. Ask whether the group is captive-bred or wild-caught and what water it has been living in. This helps plan the transition. Plants from other regions can serve perfectly well as practical aquarium planting, but such a combination should not be presented as an exact reconstruction of a natural collection site.

Aquarium and layout

Use at least 60 cm aquarium length and approximately 30 cm front-to-back floor space as a starting point for a single shoal. A short, tall tank does not provide equivalent swimming space. Additional fish groups need more room; the smallest recommended footprint is not permission to combine several shoals. We do not state a separate minimum volume without sufficient species-specific support. Always consider the actual layout and the entire adult population.

Cryptocorynes provide sheltered margins and broad leaves. Leave an open central area between plant groups. Floating plants can soften the light, provided enough surface remains open. Gentle, dispersed filter flow prevents the shoal from being continually pushed out of quiet areas. Use a biologically mature filter and a well-fitting cover. If bright lighting keeps fish permanently at the back, provide more cover before trying to lure them forward with extra food. Maintenance access must remain possible throughout a planted aquarium.

Water conditions

Our conservative starting profile is 24–28 °C, pH 6–6.5 and GH 1–10. Sources give distinctly different pH ranges. The narrower range in the overview does not prove that stable, near-neutral water is unsuitable for every espei. Origin, previous housing and acclimatisation remain important. Do not abruptly lower pH because a chart shows a lower number; first check the supplier's water and the requirements of all inhabitants.

No separate species-specific KH minimum has been established here. Very soft water requires particular attention to buffering, because small changes can have greater effects. Measure replacement water temperature, pH and hardness and make water changes under suitable, gradually adjusted conditions. Ammonia/ammonium and nitrite must not accumulate to harmful levels. Adding a new shoal requires monitoring of filter load even in an established tank. Avoid food deposits between broad leaves and record changes in breathing, appetite and hiding.

Behaviour and group size

A group of ten or more is a useful target in an appropriately sized aquarium. Numbers do not replace space: ten espei plus ten larger harlequins are a different stocking proposition from a single small shoal. These fish mainly use the middle and upper water layers. They need not remain in a tightly synchronised formation all day. Quietly searching for food among plants can be normal; isolation combined with refusal to eat or clamped fins deserves attention.

Harlequin rasboras are conditionally suitable companions if both species retain their own groups and have additional swimming space and several feeding spots. The larger species must not repeatedly displace the smaller espei. Avoid large predatory fish and extremely boisterous feeders. A peaceful label does not rule out food competition. Assess a combination during meals and after the fish mature, rather than solely by overlapping water values. Tiny shrimplets cannot be guaranteed safety alongside fish that take small animal food particles.

Feeding

Specialist accounts describe the natural diet as probably consisting of small invertebrates. Suitable dry foods are accepted in aquaria. Offer a complete food in small, readily swallowed pieces and add variety with appropriately small live or frozen foods. The small mouth remains the practical limitation: a large flake does not become suitable because the packaging mentions small tropical fish. Crush it when necessary and watch whether the fish actually swallow it.

Distribute modest portions across quiet feeding spots. In mixed shoals, faster, larger fish often reach food first; adding more food cannot replace better distribution. Dried Daphnia can provide a supplement, crushed if necessary, but is not a complete staple diet. The linked Supervit flakes are complete food; the linked water fleas play a supplementary role. Do not leave food on the bottom assuming these midwater fish will always clear it later. Persistent spitting calls for a change in particle size or food choice.

Breeding

Lambchop rasboras attach adhesive eggs to plant leaves. The familiar upside-down spawning beneath a leaf is characteristic of this group; spawning on the upper surface has also been described for this species. Broad leaves with accessible surfaces are therefore more useful than an arbitrary layer of gravel alone. The parents do not guard the eggs and may eat them. A quiet, separate breeding setup provides more control than a busy community aquarium.

Soft, acidic conditions are described for deliberate breeding, but this is not an instruction to rapidly alter the entire community tank. Prepare the breeding aquarium and very small first foods beforehand. Protect fry from filter intakes and match food size to their development; newly hatched Artemia are not automatically the correct first food. Observing spawning does not guarantee surviving young. Examine eggs and larvae gently and minimise disturbance. Planning suitable care for the offspring in advance prevents a successful spawning from ending through lack of appropriate food.

Sources & review

This care guide draws on several specialist sources and was last checked on .

View the sources