Taxonomy & naming
Rasbora patrickyapi was formally described by Heok Hee Tan in 2009 from material collected in the Katingan and Kahayan river basins of central Kalimantan, Indonesian Borneo. The species belongs to the genus Rasbora, one of the most speciose cyprinid genera in Southeast Asia, which has served as a catch-all for small, slim, schooling cyprinids across the region. Over recent decades, systematic revision has carved a number of genera out of Rasbora — among them Boraras (the miniature peat-swamp rasborins), Trigonopoma, Brevibora, Kottelatia and Rasboroides — but patrickyapi remains placed in Rasbora sensu stricto, in line with the treatment recorded in the primary description and consistent with the Catalog of Fishes (Eschmeyer, CAS), the governing authority for valid names.
The specific epithet honours Patrick Yap, acknowledging his contributions to Singaporean and Bornean freshwater fish research. No recognised subspecies or geographic variants have been described.
Morphology
Rasbora patrickyapi is a slender, moderately laterally compressed cyprinid with a maximum recorded standard length of 2 in, though most wild individuals are somewhat smaller. The fin-ray formula is characteristic of the genus: dorsal soft rays 9, anal soft rays 7. The body is elongate and torpedo-shaped, reflecting the active schooling habits typical of Rasbora.
The coloration in life features the lateral patterning common to many blackwater-dwelling Bornean rasborins, with the precise pigment detail described in the original 2009 treatment. As with many peat-swamp species, live colour can appear muted in photographs; captive specimens in appropriately dimly lit, tannin-stained water show fuller expression of their natural markings.
Habitat
The species is known from the Katingan and Kahayan river basins of central Kalimantan, where it occupies shallow, slow-flowing swampy areas immediately adjacent to flowing blackwater streams within lowland peat-swamp forest and degraded heath forest. The substrate beneath these marginal pools and channels consists of a mixture of peat and silica sand, overlaid with accumulations of decomposing leaf litter and woody debris.
The water is characteristically soft and extremely acidic, stained deep brown by humic and fulvic acids leaching from the peat. Natural conditions centre on temperatures between 23 and 81 °F, with pH values well below 7 — often in the low-acid range typical of Sundaland peat swamps. Dissolved mineral content is very low, consistent with the near-distilled precipitation that feeds these systems through the peat matrix. The fish is benthopelagic, living and feeding in the lower and mid water column of these shallow, tannin-stained pools.
Feeding
Like other members of the genus Rasbora, patrickyapi is an opportunistic omnivore, taking small invertebrates, insect larvae and other zooplankton available in the leaf-litter-rich water column of its peat-swamp habitat. The rich decomposing substrate of these blackwater environments supports a community of small chironomid larvae, microcrustaceans and other invertebrate prey that form the primary diet of small rasborins.
In the aquarium the species accepts standard micropredator foods including frozen daphnia, cyclops, bloodworm and brine shrimp nauplii. Small, high-quality dry foods are also taken once the fish settles. Given the species' association with very clean, low-bacterial-pressure blackwaters, overfeeding must be avoided — uneaten food deteriorates water quality quickly in the soft, poorly buffered conditions it requires.
Mating
Rasbora patrickyapi is an egg-scattering, non-guarding spawner in the manner typical of the genus Rasbora and the wider danionin clade. No nest is built and no form of parental care is given. Courtship follows the standard rasborin pattern: a driving male pursues a gravid female through vegetation and leaf litter, the pair moving rapidly before pressing together to release eggs and milt simultaneously.
The adhesive or weakly adhesive eggs fall among plant roots, moss, leaf litter and into the peat substrate where they rest until hatching. The adults take no further interest in the eggs and will consume them if given access, which is the universal condition among Rasbora.
Breeding
No detailed captive-breeding account for Rasbora patrickyapi has been published, but the spawning biology is expected to follow the general Rasbora model: egg-scattering over fine-leaved plants, moss or leaf litter in shallow water, with the eggs left entirely unguarded after deposition. A soft-water conditioning period, live or frozen food and a gentle temperature rise are likely prerequisites.
Breeders attempting this species should replicate the species' natural chemistry as closely as possible — very soft, acidic water (pH well below 7, very low hardness) with a tannin-stained appearance from Indian almond leaves, alder cones or peat filtration. A shallow breeding vessel with a fine-leaved plant mat or spawning mop, from which adults are removed after spawning, follows the practice proven for other peat-swamp rasborins. Fry are expected to be small and best started on infusoria or commercially prepared fry food before progressing to newly hatched brine shrimp.
In the aquarium
Aquarium Glaser notes that Rasbora patrickyapi requires informed aquarists willing to invest in careful water-chemistry management and is considered moderately difficult. The key requirement is very clean, extremely soft and acidic water replicating the peat-swamp environment: the addition of decaying leaves such as Indian almond (Terminalia catappa) and alder cones is recommended, along with peat filtration or RO-prepared water, to achieve the low mineral content and tannin staining the species needs.
The fish should be kept in a group of at least six to eight individuals in a well-planted, dimly lit tank with dark substrate and gentle filtration. Tankmates should be chosen carefully from other small peat-swamp species tolerant of the same water chemistry — blackwater rasborins, small Sundaic bettas or other Bornean cyprinids are appropriate companions. Bacterial load must be kept very low; a mature, lightly stocked tank with excellent biological filtration and minimal organic waste is essential. Given its restricted natural range and Near Threatened status, captive populations have real conservation value, and responsible documentation of successful spawning is encouraged.
Conservation
The IUCN Red List assessed Rasbora patrickyapi as Near Threatened in January 2019, under criteria B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv), indicating a restricted range and continuing decline in the extent and quality of its habitat. The species is known only from the Katingan and Kahayan river basins of central Kalimantan, making it entirely dependent on the peat-swamp and heath-forest ecosystems of that region.
Those ecosystems are among the most threatened on Earth. Large-scale drainage and conversion of Bornean peat-swamp forest for oil palm and pulpwood plantations, combined with devastating peat fires during El Niño drought years, have destroyed enormous areas of the habitat on which patrickyapi and dozens of co-occurring endemic species depend. Water quality in remaining peat-swamp fragments is further degraded by agricultural runoff and sedimentation. As a species adapted to the highly specific chemistry of intact peat swamps — extremely soft, highly acidic, tannin-rich blackwater — it has essentially no tolerance for the modified, turbid or chemically altered water left behind by habitat conversion. Continued monitoring of its remaining range and protection of intact peat-swamp forest are the primary conservation imperatives.