Taxonomy & naming
Melanotaenia sneideri was described by Gerald R. Allen and Renny K. Hadiaty in 2013, in the journal aqua, International Journal of Ichthyology (volume 19, number 3, pages 137–146), from specimens collected in the Kumawa Mountains of West Papua Province, Indonesia, in late March of that year. Eschmeyer's Catalog of Fishes records the valid name as Melanotaenia sneideri Allen & Hadiaty, 2013; because it was described in Melanotaenia, the genus in which it remains, the authority is cited without parentheses.
The genus Melanotaenia is the largest in the family Melanotaeniidae, the true rainbowfishes, which range across New Guinea and northern and eastern Australia. It is a morphologically conservative genus: species tend to be separated more by adult male coloration and by their isolated drainages than by meristic characters, which overlap broadly. M. sneideri is diagnosed in part by its meristics — typically five spines in the first dorsal followed by one spine and 13 rays in the second dorsal, an anal fin with one spine and around 24 rays, about 35 lateral scales, and 18 to 20 total gill rakers on the first arch — together with its bright red adult male coloration and its highly localised montane origin.
The specific epithet honours Richard Sneider, who with Max Ammer planned and carried out the 2013 Kumawa Mountains Expedition on which the species was found; Sneider discovered, photographed, and filmed the fish and, with Obed Holago, first collected the type specimens. The genus name combines the Greek 'melas' (black) with the Latin 'taenia' (band or stripe), referring to the dark lateral stripe characteristic of many species in the genus.
Morphology
Melanotaenia sneideri is a small, deep-bodied, laterally compressed rainbowfish. The original description and FishBase give a maximum length of about 3 in SL for both sexes, although an Australian government import-risk draft references a maximum of at least 3.5 in SL; the type material peaks at roughly 3 in SL in adult males. As in other Melanotaenia, the body is strongly compressed and deepens with age, with the maximum body depth of mature males reaching around 42% of standard length, giving dominant fish an almost diamond-shaped profile.
Like all members of the genus, it carries the family's divided dorsal fin — a short anterior dorsal followed by a longer posterior dorsal. Meristic counts from the original description are a first dorsal of four to six spines and a second dorsal of one spine with 13 to 14 rays (usually five spines then one spine and 13 rays), an anal fin of one spine and 23 to 28 rays (usually 24), 13 to 15 pectoral rays (usually 14), 34 to 36 lateral scales (usually 35), and 18 to 20 total gill rakers on the first arch. Vomerine teeth are absent or present only as a rudimentary patch.
The adult male's live coloration carries the species: a bright red body against a bluish head, with dark brown to blackish dorsal, anal, and pelvic fins and a pinkish-orange caudal. Females and subordinate fish are far plainer, and a male's colour intensity tracks his mood, dominance, and condition — the usual story across the genus.
Habitat
The species is known only from its type locality in the Kumawa Mountains of West Papua Province, Indonesia, at roughly 1,164 ft — a high elevation for a rainbowfish. The habitat is a small ephemeral lake basin, on the order of 1,0 ft by 1969 ft, and its character swings with the seasons. In dry periods the basin shrinks to a small, very clear creek that surfaces from limestone rocks, runs for about 1640–1969 ft, and drains back underground.
In the dry season this creek is only 3–7 ft wide, with a maximum depth of 12–19.5 in and an average depth of just 4–8 in, and the fish concentrate in rocky pools along its course. When the rains come, the water inundates the basin and the system expands into a shallow lake, allowing the fish to disperse across the flooded area. FishBase classifies the species as freshwater and pelagic, occupying a depth range of about 0–3 ft in this shallow system.
The limestone setting implies clear, mineral-rich, hard-to-alkaline water, consistent with the karstic geology of the basin. That single peculiar locality is the central fact of the species' biology: as far as anyone has documented, it lives nowhere else.
Feeding
Little has been published specifically on the diet of Melanotaenia sneideri. FishBase models its trophic level at about 2.9, indicating an omnivore, which is consistent with the feeding ecology of rainbowfishes generally.
Members of the genus are opportunistic omnivores that forage in the upper and middle water column, taking small aquatic and terrestrial invertebrates — insect larvae, small crustaceans, surface-fallen insects — along with algae and plant material grazed from submerged surfaces. In a shallow, seasonally fluctuating creek-and-pool system like the Kumawa basin, a flexible diet of that sort would suit the swings in water volume and prey between dry and wet seasons.
No aquarium feeding regime specific to this species is documented. By analogy with its congeners, captive individuals would be expected to accept a varied omnivorous diet, but no such husbandry is established for M. sneideri.
Mating
No mating behaviour has been documented specifically for Melanotaenia sneideri; the species is newly described, exceptionally rare, and essentially unstudied in this respect. What follows is inferred from the well-known reproductive biology of the genus and should be read as such.
Rainbowfishes of the genus Melanotaenia are egg-scattering, plant-spawning fishes with no parental care. Males are social and competitive. They stake out display areas and court females with intense colour, flaring the fins and flashing the body until coloration hits maximum saturation; many species also flicker a pale 'courtship band' along the head and nape of a displaying male. Display and spawning run hardest in the hours after first light, and a male is usually at his most colourful when rivals are watching.
Whether M. sneideri follows this pattern in detail is unrecorded, but its strongly dimorphic adult male coloration is consistent with the visual, display-driven courtship seen across the genus.
Breeding
There is no documented account of breeding in Melanotaenia sneideri, in the wild or in captivity, and no aquarium strain is known. Given that the species is Critically Endangered and very rarely, if ever, kept, this section necessarily draws on the general breeding biology of the genus rather than on observations of this fish.
Rainbowfishes of the genus Melanotaenia are continuous or near-continuous spawners when conditions are good. Females release a few adhesive eggs at a time over fine-leaved vegetation, the eggs hanging by fine filaments from the spawning medium; rather than a single large clutch, a female may drop a handful of eggs daily over a long spawning stretch. Adults give no parental care and will eat their own eggs and fry. Genus eggs generally hatch after a week or more at tropical temperatures, producing tiny fry that hang near the surface and need very small first foods before they can take larger fare.
In the seasonal Kumawa habitat, the inundation of the basin during the rains would plausibly provide the expanded, vegetated shallow-water conditions in which spawning and fry survival are most favourable, but this is an inference rather than a documented life-history observation for the species.
In the aquarium
Melanotaenia sneideri is, for practical purposes, not an aquarium fish. As a newly described, Critically Endangered species known from a single remote montane locality, it has no established presence in the hobby and no documented species-specific care or breeding records. An Australian import-risk assessment has considered the species, and FishBase notes only a generic potential for aquarium use; there is no aquarium strain in circulation.
No species-specific husbandry guidance exists; only genus-level care can be offered with any confidence. Rainbowfishes are peaceful, active schoolers that do best in groups in a long tank with open swimming space, take a varied omnivorous diet, and favour warm, soft-to-moderately-hard, slightly alkaline tropical water. The limestone, high-altitude origin of M. sneideri points further toward clear, hard, alkaline water and perhaps cooler temperatures than many lowland rainbowfishes — but these are inferences from habitat, not tested parameters.
Its conservation status argues for restraint. It is documented here for completeness, not recommended as a fish to seek out or keep.
Conservation
Melanotaenia sneideri is assessed as Critically Endangered (CR) on the IUCN Red List, under criterion B2ac(i), with the assessment dated 6 December 2019 (Red List version 2025-2; species ID 161111171). It is not evaluated under CITES.
The listing reflects extreme range restriction: the species is known from one tiny type locality — a single ephemeral lake basin and its limestone creek in the remote Kumawa Mountains of West Papua — and so has a very small area of occupancy. A fish confined to one hydrologically distinctive basin has essentially no buffer against local disturbance, habitat change, or chance events, with no documented outlying population to fall back on.
Remoteness buys some incidental protection from collectors, but the same isolation means the entire known global population rides on the health of one montane water system. For a fish this narrowly endemic, protecting that single basin and its odd seasonal hydrology is much the same as protecting the species.