Taxonomy & naming
Melanotaenia veoliae was described in 2012 by Kadarusman, Renny K. Hadiaty, G. Segura, G. Setiawibawa, Domenico Caruso and Laurent Pouyaud in a paper titled 'Four new species of Rainbowfishes (Melanotaeniidae) from Arguni Bay, West Papua, Indonesia,' published in the journal Cybium (volume 36, issue 2, pages 369–382). It was one of four rainbowfishes newly described together from the Arguni Bay area of the Bird's Neck region. Eschmeyer's Catalog of Fishes, the authority for valid names, records the species under the short-form authority Kadarusman, Caruso & Pouyaud, 2012; because it was described directly in Melanotaenia, no parenthetical authority is used.
The genus Melanotaenia is the largest in the family Melanotaeniidae, the true rainbowfishes, which radiate across New Guinea and northern and eastern Australia within the order Atheriniformes (the silversides). Within this large genus, M. veoliae was diagnosed from its congeners in the Bomberai Peninsula and Bird's Neck region by a combination of meristic and morphometric characters rather than by a single striking trait — a typical situation in Melanotaenia, where many species overlap in counts and are separated only by character combinations.
The specific epithet honours the Foundation Veolia Environment of France, which sponsored the Lengguru-Kaimana Expedition of October–November 2010 during which the type material was collected. The genus name combines the Greek 'melan' (black) with the Latin 'taenia' (stripe or band), referring to the dark lateral stripe seen in many species of the genus.
Morphology
Melanotaenia veoliae is a small rainbowfish, reaching about 3.5 in in standard length in the largest recorded specimens. The body is fusiform and laterally compressed, of normal proportions for the genus rather than notably deep-bodied, and carries the family's characteristic divided dorsal fin — a short anterior dorsal followed by a longer posterior dorsal — together with a long-based anal fin.
The meristic detail anchors the species. The dorsal fin bears IV–V spines in the first dorsal and I spine with 12–13 soft rays in the second; the anal fin has I spine and 22–27 rays. There are 34–37 lateral scales, 10–11 transverse scales, 17–18 predorsal scales, 12–14 cheek scales, and 18–20 gillrakers. Morphometric features used to separate it from neighbouring Bomberai and Bird's Neck congeners include a snout length of 8.0–9.1% of standard length, eye diameter 6.3–7.9% of standard length, and caudal-peduncle depth of 16.5–17.7% of standard length.
Detailed live-colour notes for this rarely seen species are sparse beyond the original description, and no large body of aquarium photography exists to refine them. As with rainbowfishes generally, breeding males would be expected to be the more colourful and possibly the deeper-bodied sex, but specific, confirmed dimorphism data for M. veoliae are limited — the published record emphasises meristics and proportions over colour.
Habitat
Melanotaenia veoliae is known from Gebiasi Creek on the Bomberai Peninsula in the Arguni Bay / Bird's Neck region of Papua Barat (West Papua), Indonesia. The type locality is a fragmented hydrologic system set in karst. The creek emerges from a cave, flows in the open for roughly 197 ft, then disappears into a subterranean outlet before reappearing among mangroves about 656 ft further on. The species inhabits the aerial (surface) portion of this river.
Where it runs in the open, Gebiasi Creek is described as a blue, crystalline stream flowing through primary forest — narrow, only about 7–10 ft wide, and shallow, up to roughly 3 ft deep. This is a benthopelagic freshwater species of tropical climate. A partly subterranean drainage and a very short aerial reach leave the available habitat genuinely tiny, which is the dominant theme of the species' ecology.
Specific physico-chemical measurements (precise temperature, pH, and hardness ranges) for Gebiasi Creek are not well documented in the accessible record, so detailed water-chemistry figures here are data-sparse. Karst-fed streams in this region tend to run clear and mineral-rich, consistent with the crystalline appearance noted in the field, but published numbers specific to M. veoliae's water remain limited.
Feeding
No diet study specific to Melanotaenia veoliae has been published, and FishBase records a modeled trophic level of about 2.9, which places it as a low-level omnivore. In the absence of species-specific gut-content data, its feeding ecology is best inferred from the genus: Melanotaenia rainbowfishes are opportunistic omnivores that forage in the upper and middle water column.
In comparable rainforest and karst streams, the natural diet of small Melanotaenia comprises small aquatic and terrestrial invertebrates — insect larvae, small crustaceans, and insects taken at or near the surface — supplemented with algae and fine plant or detrital material. A narrow, fast-draining karst creek of the kind M. veoliae occupies would be expected to deliver a steady supply of drifting and surface-falling invertebrates from the surrounding primary forest.
Because this species is seldom if ever kept, captive feeding notes are genus-level rather than veoliae-specific: rainbowfishes generally take flake, micro-pellets, and live or frozen foods readily. Any such guidance should be applied with caution given the absence of confirmed husbandry data for this particular species.
Mating
There are no published observations of courtship or mating behaviour specific to Melanotaenia veoliae; FishBase carries no reproduction data for the species. What can be said responsibly is drawn from the well-documented reproductive biology of the genus rather than from direct observation of this fish.
Melanotaenia rainbowfishes are egg-scattering, plant-spawning species without parental care. Males are typically social and competitive, courting females with colour displays in which the body's hues intensify; in many species a flickering pale 'courtship band' flashes along the head and nape of a displaying male, and display activity peaks in the early morning. Whether M. veoliae follows this pattern in detail is unconfirmed, but it is the expected mode for the genus.
Given the species' minute and fragmented karst habitat, its breeding sites in the wild are presumably confined to the short aerial reach of Gebiasi Creek among submerged roots, vegetation, or fine substrate. Beyond that inference, mating specifics for M. veoliae are genuinely data-sparse.
Breeding
No captive breeding of Melanotaenia veoliae has been documented, and the species appears to be essentially absent from the aquarium hobby — a consequence of its very recent description and its remote, single-creek distribution. As a result there are no veoliae-specific data on clutch size, egg characteristics, incubation period, or fry development.
If the species behaves like its congeners, it would be expected to be an egg-scatterer depositing small, adhesive eggs that attach by fine filaments to fine-leaved plants or spawning media, with spawning spread over many days and a female releasing a few eggs at a time rather than a single clutch. Rainbowfish eggs of this type typically hatch after roughly one to two weeks at tropical temperatures, and the adults provide no care and may consume their own eggs.
These statements are offered strictly as genus-level expectations. Until the species is bred or studied in detail, its breeding biology should be regarded as unknown rather than established, and any husbandry attempt would be working without a confirmed protocol.
In the aquarium
Melanotaenia veoliae is, for practical purposes, not an aquarium fish: it is a rare, very recently described karst-creek species that has not entered the hobby in any meaningful way, and no dedicated husbandry account for it could be located. FishBase notes only a general 'aquarium potential.' Any keeping notes are therefore extrapolated from the genus and should be applied with explicit caution.
Melanotaenia in general are hardy, peaceful, shoaling fishes best kept in groups of six or more, in tanks with a long open swimming lane and stable, well-filtered water. They are active swimmers that show their best colour when several individuals are kept together so that males display. As omnivores they accept flake, micro-pellets, and live and frozen foods.
For a small karst-stream species, clear, well-oxygenated, mineral-rich water at tropical temperatures would be a reasonable starting point by analogy with its habitat, but the absence of confirmed water parameters for Gebiasi Creek means even this is provisional. Because the wild population is restricted and assessed as Vulnerable, there is also a conservation argument against any wild-collection pressure for the trade; this is a species better left studied in situ than pursued for the aquarium.
Conservation
Melanotaenia veoliae is assessed as Vulnerable (VU) on the IUCN Red List under criterion D2. The D2 listing reflects a very restricted range concentrated at essentially a single location — the small Gebiasi Creek karst system in West Papua — which makes the species susceptible to a single threatening event such as habitat alteration, pollution, or hydrological disruption of the karst drainage.
The entire known range is a short aerial reach of one karstic creek, with the watercourse otherwise running underground. A species confined to so small and so specialised a habitat has little resilience: there is no large outlying population to buffer a local decline, and a single disturbance to the creek or its catchment could affect the whole known population at once. FishBase nonetheless lists the species as of medium resilience on demographic grounds, with a modeled population doubling time of 1.4–4.4 years, and notes it poses no threat to humans.
There is no evidence of significant collection pressure for the trade, since the species is effectively absent from the hobby, so the principal conservation concern is the integrity of its tiny karst habitat rather than over-harvest. The most useful contribution aquarists and hobbyists can make is to avoid creating demand for wild-caught specimens of so narrowly endemic a fish.