Taxonomy & naming
The redstripe rasbora was originally described as Rasbora pauciperforata by Max Weber and Lieven Ferdinand de Beaufort in 1916, from type material collected at Gunung Sahilan and Deli in Sumatra, Indonesia. The genus Rasbora as it stood through most of the twentieth century was a large, heterogeneous assemblage of small Asian cyprinids, and ichthyologists increasingly recognised that it was not a natural (monophyletic) group.
Phylogenetic revision eventually dismembered the old Rasbora, carving out several new genera including Trigonopoma, Boraras, Brevibora and Kottelatia. Trigonopoma pauciperforatum — note the corrected spelling pauciperforatum in the current combination — is the valid name recognised by the Catalog of Fishes (Eschmeyer, CAS), the governing authority for valid names used on this site. The old combination Rasbora pauciperforata still appears in legacy literature and dealer lists. The family placement is Danionidae (sometimes treated as the subfamily Danioninae within the broader Cyprinidae), confirmed by mitochondrial genomic data.
The genus name Trigonopoma is derived from Greek trigonon (triangle) and poma (cover, opercle), referring to a feature of the opercular region. The specific epithet pauciperforatum is Latin for 'few-pored,' alluding to the reduced lateral-line pore count — the lateral line in this species is incomplete, a character used in its original description.
Morphology
Trigonopoma pauciperforatum is a slender, laterally compressed cyprinid reaching a maximum of about 3 in standard length, though most wild and aquarium individuals are smaller. The body is typical of the slim, schooling rasboras: torpedo-shaped with a slightly pointed snout, a small terminal to subterminal mouth, and a deeply forked caudal fin.
The defining feature is the broad, intensely coloured lateral stripe running from the rear of the opercle to the caudal peduncle, which in life shows as a bright orange-red to crimson band. Above this stripe the back is olive-brown to greenish; below it the flanks are silvery, and the belly is pale. The stripe colour intensifies markedly in males when in peak condition or displaying to rivals, earning the species its common names. The lateral line is incomplete — reduced to the first few scales behind the head — which is the character behind the species epithet.
Sexual dimorphism is moderate. Males are slimmer and display more vivid stripe colouration, particularly during courtship, while females are deeper-bodied and more silvery overall, becoming noticeably rounded in the abdomen when carrying ripe eggs.
Habitat
This species is quintessentially a Sundaland blackwater fish. In the wild it inhabits slow-moving to standing forest streams, peat-swamp margins, and shaded pools beneath closed-canopy tropical forest in Peninsular Malaysia, Sumatra (from the Siak River in Riau province south to the Musi River in South Sumatra), Borneo and parts of mainland Southeast Asia including the Mekong drainage of Cambodia and possibly Thailand. The GBIF record places the type locality in central Sumatra.
Blackwater habitats of this kind are defined by the leaching of tannins and humic acids from decaying organic matter — fallen leaves, submerged roots, decomposing wood — into rivers that drain ancient peat deposits. The resulting water is soft, often extremely so, with a pH that may fall as low as 4.0 in deep peat-swamp systems, amber-coloured and low in dissolved minerals and nutrients. FishBase records a natural pH range of 5.0–6.0 for the species, with hardness around 5–12 dH. Light levels in these habitats are dim, filtered by the dense forest canopy and further attenuated by water colour.
T. pauciperforatum is a schooling, benthopelagic species found in loose groups that range through the mid and lower water column, retreating into cover among submerged roots and leaf litter when alarmed.
Feeding
Like the great majority of small rasboras, Trigonopoma pauciperforatum is a micropredator in the wild. It feeds on small invertebrates encountered in the water column and at the surface — tiny aquatic insects, insect larvae, micro-crustaceans and zooplankton drifting in the sluggish blackwater. The low productivity of peat-swamp water means food is often scarce and the fish feed opportunistically throughout the day.
In the aquarium the species is straightforward to feed but shows a marked preference for live and frozen foods. Small items such as bloodworm, Daphnia and freshly hatched brine shrimp are taken eagerly and help maintain the brilliance of the lateral stripe. Quality micro-pellets and fine flakes are accepted, particularly once the fish are settled, but live or frozen foods should form a significant part of the diet for fish in their best colour. The small mouth size means food particle dimensions matter — items suitable for a nano fish are ideal.
Mating
Trigonopoma pauciperforatum is an egg-scattering, non-guarding spawner. There is no pair bond, no nest construction and no parental care of any kind. In the wild, spawning likely takes place in seasonally warmer, flooding conditions among fine-leaved marginal vegetation and submerged root mats — a common trigger among rasboras native to monsoon-influenced or seasonal blackwater systems.
Courtship is brief and energetic. Ripe males develop intensified stripe colouration and actively pursue gravid females through the water column, displaying laterally and pressing close as the pair passes through vegetation or open water. Spawning is a rapid release of adhesive or weakly adhesive eggs and milt together, often among fine-leaved plant growth or over leaf litter. A school of fish may engage in multiple brief spawning chases over the course of several hours. Adults take no interest in the eggs and will consume them and any free-swimming fry if given the opportunity.
Breeding
The redstripe rasbora breeds as an egg-scatterer with no parental care, following the pattern of most small rasboras. Eggs are adhesive or weakly adhesive and are scattered over fine-leaved plants, moss clumps or bare substrate. Once spawning is complete, adults should be removed to prevent predation of the eggs.
A separate breeding tank is recommended, set up to mimic the species' blackwater origins: soft, acidic water (pH around 5.5–6.5, hardness well below 10 dH), dim lighting, fine-leaved plants such as java moss or floating plants, dark substrate, and a small amount of Indian almond leaf or other botanical to release tannins. A slight rise in temperature or the addition of fresh, similarly conditioned water can stimulate spawning. Eggs hatch in approximately 18–48 hours at tropical temperatures, and the larvae become free-swimming three to four days after hatching. First foods must be very small — infusoria, green water or commercially prepared fry foods — before the fry can accept newly hatched brine shrimp nauplii. Growth is moderately rapid once feeding is established.
In the aquarium
The redstripe rasbora is a specialist's fish that has long rewarded hobbyists willing to meet its specific needs. It is peaceful with similarly sized tankmates and poses no threat to other fish, but it must be kept in a proper school — a group of at least eight to ten individuals is the minimum for confident, natural behaviour and the best display of male colouration. In a large enough group the competition between males keeps their stripe colour at its most saturated.
Water chemistry is the single most important factor. Soft, acidic water — pH 4.0–7.5 is cited as the tolerance, but the species looks and behaves best at pH 5.5–6.5 with very low hardness — is essential for long-term health and for any attempt at breeding. A heavily planted tank with dark substrate, driftwood, dried leaf litter, dim lighting and gentle filtration (a sponge filter is ideal for the low-flow blackwater feel) allows the fish to show its natural behaviour and colouration. Alongside other small blackwater species — pygmy rasboras, small loaches, micro-corydoras relatives, blackwater tetras — it forms a stunning and ecologically coherent community.
Temperature should be kept in the range of 70–79 °F. The species is not particularly temperature-sensitive within that band but does not appreciate cold or strongly fluctuating conditions. It is a peaceful, long-lived fish when kept correctly, and pairs well with the growing botanical aquarium aesthetic.
Conservation
Trigonopoma pauciperforatum is assessed as Least Concern (LC) on the IUCN Red List (2022). It has a broad distribution across Sundaland — Peninsular Malaysia, Sumatra and Borneo — and portions of the Mekong basin on the mainland, and is considered widespread and common in suitable habitat with no documented major range-wide threats.
That assessment, however, must be read alongside the dramatic ongoing loss of its core habitat. Southeast Asian peat-swamp forests are among the most threatened ecosystems on Earth: large areas of Sumatra, Borneo and Peninsular Malaysia have been drained, burned and converted to oil-palm and pulpwood plantations over recent decades. Peat-swamp drainage eliminates the acidic, humic-rich hydrology that species like T. pauciperforatum require, and there is no functional substitute. Pollution from agricultural runoff and sedimentation further degrades remaining streams. While the species' broad range buffers it at the global level, local populations in heavily modified landscapes may have been substantially reduced or extirpated. Aquarium specimens are drawn from wild populations as well as from captive breeding, and the continued availability of the species in the hobby depends partly on the survival of the Sundaland peat-swamp forests where it lives.