Taxonomy & naming
Neolebias powelli was described by Guy G. Teugels and Tyson R. Roberts in 1990 and placed in the genus Neolebias, a group of small West and Central African characins within the family Distichodontidae — the same family that contains the much larger, plant-shredding Distichodus species and the deep-bodied grazing citharinids. The genus name combines the Greek neo- ("new") with Lebias, an older genus name once applied to small killifish-like fishes, reflecting a superficial resemblance rather than any close relationship.
Distichodontidae has a wide size range from Neolebias' centimetre-scale nano fish to the metre-plus reach of the largest Distichodus, and Neolebias powelli sits firmly at the small end alongside its congeners such as N. ansorgii and N. trilineatus. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises Neolebias powelli as a valid, distinct species; nothing in the available sources suggests a taxonomic revision or synonymy issue for this name.
Morphology
Neolebias powelli is a genuinely tiny characin, reaching a maximum recorded standard length of only about 0.5 in — smaller than many aquarium livebearer fry — with a body depth roughly 4 to 4.4 times the standard length and a head length around 3.2 to 3.5 times the standard length, giving it a slender, elongated silhouette rather than the deep-bodied look of its Distichodus relatives. The flanks carry 32 to 36 ctenoid (comb-edged) scales along the lateral series, and the fins are modest: 9 to 10 branched anal-fin rays and 11 to 12 branched dorsal-fin rays.
The species' most distinctive feature is a small series of 1 to 4 spots along the body that appear iridescent green in living fish and darken to black once preserved — the likely basis for the trade name "domino tetra," evoking the spotted tiles of the game. At this scale, colour and pattern are best appreciated at close range or in a well-lit, well-planted aquarium rather than from across a room.
Habitat
Neolebias powelli is known only from the Niger Delta in Nigeria, West Africa, which is also its type locality — a narrow, single-region distribution that is unusual even among small African characins and is a core reason for its elevated conservation concern. Within the delta it occupies a pelagic habitat in tropical freshwater, swimming in open water rather than hugging the substrate.
Water in its native range runs warm, in roughly the 73–79 °F band typical of lowland West African freshwater habitats. The available sources do not report detailed pH or hardness figures for the species' native water, so keepers should treat those parameters as data sparse and lean on the general Niger Delta freshwater profile — warm, tropical, and subject to the seasonal flooding typical of West African river deltas — rather than assuming the softer, more acidic blackwater conditions associated with Central African rainforest characins.
Feeding
In the wild, Neolebias powelli feeds on small insects and crustaceans typical of the invertebrate prey available in Niger Delta freshwater habitats — a diet consistent with its tiny mouth and pelagic, open-water foraging style. It is not a plant-grazer or detritivore in the way that some of its larger Distichodontidae relatives are.
In the aquarium it adapts readily to prepared foods, accepting dried flakes and pellets sized appropriately for a centimetre-scale fish, and it does noticeably better with regular small live or frozen foods such as brine shrimp, Moina and daphnia, plus bloodworms. Given its minute mouth size, food particle size matters more for this species than for almost anything else in the Piranhas & Pacus atlas — oversized flakes or pellets are simply unavailable to a fish this small.
Mating
Specific courtship behaviour for Neolebias powelli is not documented in the available sources. Hobby breeding accounts describe the species as a group spawner, with conditioned males and females spawning together within a school rather than forming an isolated pair, which is consistent with reports for other small Neolebias species and with egg-scattering characins generally.
No external sexual dimorphism is documented in the available sources; keepers report distinguishing ripe, gravid females mainly by a fuller body shape rather than by any reliable colour or fin difference.
Breeding
Neolebias powelli is reported in hobby accounts as an egg-scattering species, consistent with the general pattern for Distichodontidae, in which Distichodus and its relatives are egg-scatterers rather than nest-builders or mouthbrooders. A conditioned group spawns over fine-leaved plants such as java moss or artificial spawning mops, with the adhesive-to-semi-adhesive eggs falling through the plant mass or a mesh substrate layer, which protects them from the adults, who show no parental care and will eat eggs found in the open.
Fry reportedly emerge without special intervention in a mature, well-planted tank, feeding on infusoria before graduating to brine shrimp nauplii. That said, this account of breeding comes from a single hobby source rather than a peer-reviewed account, so treat the specifics as good practical guidance rather than an exhaustively documented protocol; the wider Distichodontidae pattern of egg-scattering with no parental care and species that are rarely bred at home is broadly consistent with what little is reported here.
In the aquarium
Neolebias powelli is about as far from the piranha stereotype as this atlas gets: a peaceful, genuinely tiny nano fish that belongs in a species-appropriate nano or well-planted aquarium rather than anything resembling a predator tank. A school of ten or more is recommended to bring out natural shoaling behaviour and reduce stress, and dense planting — particularly fine-leaved species such as java moss — gives the fish cover and doubles as a spawning substrate.
Because of its minute size, tankmates must be chosen with real care: anything large enough to see it as food, or boisterous enough to outcompete it at feeding time, is unsuitable. Warm water in the 73–79 °F range suits it well. Prospective keepers should also weigh the conservation angle directly: this is an Endangered species known from a single delta system, so sourcing captive-bred stock rather than wild-caught fish, where available, is the more responsible choice.
Conservation
Neolebias powelli is assessed by the IUCN Red List as Endangered, reflecting a high risk of extinction in the wild tied to its extremely restricted range — it is known only from the Niger Delta in Nigeria. A single-region endemic freshwater fish in the Niger Delta faces a familiar cluster of pressures in that landscape, including oil-industry pollution, habitat degradation and wetland loss, though the available sources do not itemise a specific, sourced list of threats for this species beyond the Endangered status itself.
Given the narrow range and elevated threat status, this is a species where captive breeding and hobbyist propagation — the domino tetra is reportedly bred in aquaria via egg-scattering over fine plants — carries real conservation value by reducing pressure on wild populations, even though it remains a minor presence in the aquarium trade relative to larger, more commercially farmed characins.