Taxonomy & naming
Melanotaenia jakora was described in 2023 by Johannes A. Graf, Henderite L. Ohee, Fabian Herder and Haryono, in the journal Fishes of Sahul (37(2): 2063–2068), based on material from Western New Guinea. The species had circulated in the aquarium hobby beforehand as an undescribed locality form labelled Melanotaenia sp. 'Kali Jakora', and the formal description gave that trade name a valid scientific footing. Eschmeyer's Catalog of Fishes, the governing authority on valid names, records it as Melanotaenia jakora Graf, Ohee, Herder & Haryono, 2023; because it was described directly in Melanotaenia, no parenthetical authority applies.
The genus name Melanotaenia combines the Greek melan, 'black', with the Latin-form taenia, 'stripe' or 'band', a reference to the dark lateral band typical of many species in the genus. The specific epithet jakora derives from Jakora village, the nearest named settlement to the type locality: the holotype and paratypes were collected from a small rainforest creek crossing the road from Meyado to Jakora. The genus Melanotaenia is the largest in the family Melanotaeniidae, the true rainbowfishes of the order Atheriniformes, a group that radiates across New Guinea and northern and eastern Australia.
Within the genus, M. jakora is diagnosed more by colour pattern and fin shape than by meristics, which overlap broadly across rainbowfishes. Its distinguishing combination includes the absence of dark scale margins, a reflective blue body shine, a solid uninterrupted midlateral stripe, and dorsal and anal fins that become elongated in adult males, their tips reaching back to the caudal-fin base. Reported fin-ray counts are four to six dorsal spines and nine to twelve dorsal soft rays, with a single anal spine and eighteen to twenty-two anal soft rays.
Morphology
Melanotaenia jakora is a small, laterally compressed rainbowfish, reaching a maximum recorded length of about 2.5 in SL — a dwarf by the standards of a genus whose larger members exceed 4.5 in. In aquarium conditions it is reported at roughly 2.5–3 in. The body is compressed in the family pattern, and the species carries the divided dorsal fin characteristic of Melanotaenia, with a short anterior dorsal followed by a longer posterior dorsal.
Colour is subtle rather than gaudy. The body shows a reflective blue shine over a soft grey to pinkish ground, with sparkling blue-white highlights along the scales — the feature behind its 'Sparkle' trade name — and a solid, uninterrupted dark midlateral stripe running the length of the flank. Unlike many congeners, it lacks dark scale margins, which contributes to the clean, polished look of the sides. Brief colour flashes appear in the fins during activity and display.
The clearest sexual character is fin development. In adult males the dorsal and anal fins are elongated, their trailing tips extending back to the base of the caudal fin, whereas females retain shorter, more rounded fins. Reported meristics include lower-limb gill rakers on the first arch numbering around fourteen (range eleven to seventeen), consistent with a small, omnivore-leaning rainbowfish (trophic level roughly 2.9).
Habitat
The type locality of Melanotaenia jakora is a small rainforest creek crossing the road from Meyado to Jakora village, in Papua Barat Province, Western New Guinea, Indonesia. Collection references associate the species with the Sebjar River system. It is a freshwater, benthopelagic fish of shallow water, recorded at depths of 0–3 ft, occupying both shaded reaches beneath intact forest canopy and more open, disturbed sites along the same creek.
The habitat is true blackwater. The creek water is dark and tannin-stained, running over a muddy substrate with no submerged aquatic vegetation. Field measurements at the type locality were warm and extremely soft and acidic: a temperature of 80 °F, conductivity of just 30 µS, a pH of 6.4, and hardness below the threshold of measurability. These figures describe a low-mineral, soft-acidic environment shaped by leaf litter and forest runoff rather than by a mineral catchment.
The only fish found alongside it at the type locality was another, unidentified Melanotaenia species, underlining how species-poor these shaded forest creeks can be. The very soft, acidic, tannin-rich character of the wild water is the authoritative reference point for the species' chemistry; some hobby sources cite broader or even alkaline preferences, but those conflict with the field data from the description and should be treated with caution.
Feeding
Like rainbowfishes in general, Melanotaenia jakora is an opportunistic omnivore, its trophic level of about 2.9 placing it slightly toward the carnivorous side of omnivory. In its forest-creek habitat the natural diet would consist of small aquatic and terrestrial invertebrates — insect larvae, tiny crustaceans, and insects taken at or near the surface — supplemented by such algae and organic detritus as the tannin-shaded, vegetation-poor creek provides.
In the aquarium it is undemanding and accepts a wide range of prepared and live foods. Hobby care notes recommend fine flake and micro pellets sized for a small mouth, together with frozen and live foods such as brine shrimp, Daphnia, Cyclops, bloodworm, and mosquito larvae. A varied diet with a meaningful live or frozen component supports both colour and breeding condition.
As a small, active mid- to upper-water feeder, it does best with small amounts offered several times a day rather than a single large feeding, which suits its continual foraging behaviour and reduces waste in the soft, lightly buffered water it prefers.
Mating
Detailed reproductive observations specific to Melanotaenia jakora are sparse, as the species was only formally described in 2023. Its behaviour is best understood by reference to the well-documented pattern shared across the genus, tempered by what hobby keepers have reported for this fish.
Rainbowfishes are egg-scattering, plant-spawning species without parental care, and males court females with colour and fin displays. In M. jakora the male's elongated dorsal and anal fins, together with the reflective blue body shine, are presumed to function in display; hobby accounts note that males show best in the presence of both females and rival males in a mature, subdued-lit planted tank, which is consistent with the competitive male display typical of the genus.
As in other rainbowfishes, display and spawning activity is expected to peak in the morning hours, with a receptive female following a displaying male into fine cover to release eggs. Keepers are advised to maintain the fish in groups of at least six, and ideally eight or more, so that this social display behaviour can develop and the fish can be seen at their best.
Breeding
No species-specific captive-breeding protocol for Melanotaenia jakora is well established in the literature; the account here draws on the consistent breeding biology of the genus, applied to this species' soft-acidic origins. Rainbowfishes are continuous spawners under good conditions, depositing small, adhesive eggs that hang by fine filaments from fine-leaved plants or synthetic spawning mops, with a female releasing a few eggs at a time over many days rather than a single clutch.
For M. jakora, condition the fish in soft, slightly acidic, tannin-tinted water that mirrors the wild type locality; hobby sources note that softer water is preferred for conditioning and breeding. Adults offer no parental care and will consume their own eggs, so breeders typically transfer mops or eggs to a separate rearing container. At warm temperatures the small eggs hatch after roughly a week to a week and a half, in line with the genus.
The fry are tiny and hang near the surface at first, requiring very small first foods such as infusoria, rotifers, or liquid fry preparations before they can take newly hatched brine shrimp and finely crushed flake. Growth is gradual, and the male's elongated fins and full body sheen develop only with maturity, so it takes time to bring fish to their adult form.
In the aquarium
Melanotaenia jakora is a small, peaceful, social shoaling rainbowfish well suited to a mature community aquarium. Hobby care profiles describe it as a mid- to upper-level swimmer that should be kept in groups of at least six, ideally eight or more, where males display best against females and rival males. A tank of around 25–30 US gal is a sensible minimum, with a longer footprint preferred to give this active swimmer room; as a rainbowfish it can jump, so a secure, well-fitted lid is essential.
Water chemistry should follow the species' blackwater origins. The wild type locality was very soft, acidic and tannin-stained (pH 6.4, conductivity 30 µS, around 79 °F), and a mature, stable aquarium with a darker substrate, leaf litter or botanicals, and subdued lighting recreates that softly lit blackwater look while showing the fish's blue sheen to advantage. Reported hobby ranges are broader — roughly 73–81 °F and pH 5.5 to 7.2, with soft to moderately hard water tolerated — but soft, gently acidic water remains the authoritative target, and conflicting alkaline-preference claims from some sources should be disregarded.
It is a genuine community fish. Suitable tankmates include other small rainbowfishes, peaceful rasboras and tetras, Corydoras, small loaches, and dwarf cichlids. The species turns up only occasionally in the trade, usually as captive-bred stock, and does best in a stable, well-established planted tank.
Conservation
Melanotaenia jakora has not been evaluated by the IUCN Red List. As a species described only in 2023, it carries a status of Not Evaluated (NE) in FishBase (Red List version 2025-2), and it is likewise Not Evaluated under CITES and CMS. No dedicated IUCN assessment page exists for the species at present.
The absence of a formal assessment should not be read as evidence that the species is secure. It is, on current knowledge, a narrow-range endemic of small rainforest creeks in one part of Papua Barat Province, and narrowly distributed New Guinea rainbowfishes are, as a group, vulnerable to habitat disturbance — logging, road construction, agricultural clearance, and the siltation of tannin-stained forest creeks. The type-locality account itself notes that the species occurs in both shaded forest and 'open disturbed' sites, a hint that its habitat is already subject to human modification.
A mitigating factor is the aquarium trade's reliance on captive-bred fish: M. jakora is usually offered as tank-bred stock, which reduces collection pressure on wild populations and helps maintain the species in captivity. Until a formal evaluation is carried out, a precautionary view — treating the species as a potentially sensitive narrow endemic and favouring captive-bred fish — is the appropriate one.