Taxonomy & naming
Nannocharax hastatus was described by Kevin W. Conway, Jean Claude Jerep and Richard P. Vari — the 2014 paper is credited in the literature to Jerep & Vari — in a Copeia paper covering new species of Nannocharax from the northwestern Congo basin. It belongs to the family Distichodontidae within the order Characiformes, and to the genus Nannocharax, a large assemblage of small, elongate, bottom-associated African characins that the Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises as distinct from the deeper-bodied, more heavily built Distichodus and from the deep-bodied grazing citharinids in the sister family Citharinidae.
The type locality is the Lekoli River in the Likouala drainage of the Republic of Congo, and the original description separates N. hastatus from close congeners — notably N. ocellicauda and N. maculicauda — using lateral-line scale counts and circumpeduncular scale counts, along with its distinctive, nearly unpigmented body marked mainly by dark lines along the fin bases and a dark spot on the caudal peduncle. As with many recently described small-bodied African characins, no vernacular or trade name has taken hold for this species; it is known in the hobby and literature by its scientific name only.
Morphology
Nannocharax hastatus is a genuinely tiny fish: the original description and FishBase both record a maximum size of only about 1.5 in standard length, placing it among the smaller members of an already miniature genus (related species such as N. brevis and N. fasciatus reach roughly 2 in). The body is slender and elongate rather than the deep, compressed shape typical of Distichodus, with an inferior, slightly flattened mouth suited to picking at surfaces rather than grazing whole plants or striking at prey.
Colouration is understated: the body is described as nearly unpigmented or translucent, with the species' most distinctive marks being dark lines running along the bases of the fins and a dark spot at the caudal peduncle, features used alongside scale counts to separate it from its closest relatives. This muted, cryptic patterning is consistent with a small fish living low in the water column over rocky or sandy stream substrate rather than a fish that relies on bold display colouration.
Habitat
The species is known from the Likouala drainage in the Republic of Congo, including the Lekoli River type locality and the wider Likouala system, as well as from Pool Malebo and the Momboyo river basin (the Luilaka and Tshuapa rivers) in the Democratic Republic of Congo — all within the northwestern portion of the greater Congo River basin. FishBase lists it as a freshwater pelagic species, though the genus as a whole, and congeners such as N. brevis, are typically associated with swift-flowing river sections with rocky substrates and marginal vegetation rather than still water.
No temperature or pH range has been recorded for N. hastatus specifically in the sources available for this account. Congeneric species from across the wider Nannocharax range, from Senegal to Cameroon and the Congo basin, are associated with warm African river conditions typical of the Congo system, but assigning specific numbers to this species would be guesswork rather than documented fact, so none are given here.
Feeding
No diet study specific to Nannocharax hastatus has been located. At the genus level, Nannocharax species are omnivorous small-stream fish that feed on small invertebrates and on vegetation and algae picked from rocky or sandy substrate, consistent with FishBase's mid-level trophic score of 3.1 recorded for this species (indicating a mixed diet rather than a strict predator or strict herbivore).
In the aquarium, congeners in the genus are kept on a varied diet of small live and frozen invertebrate foods (such as micro worms, daphnia and cyclops) alongside algae-based or vegetable-inclusive foods, reflecting that same omnivorous, substrate-picking feeding style. No aquarium feeding data exists specifically for N. hastatus, as the species does not appear to be established in the hobby.
Mating
No courtship or spawning behaviour has been documented for Nannocharax hastatus. At the genus level, males of related Nannocharax species are reported to be more colourful than females and to display to one another, but this has not been confirmed for N. hastatus itself, and no external sexual dimorphism has been described for this species in the available literature.
Breeding
Breeding has not been documented for Nannocharax hastatus, and it does not appear to be established in the aquarium trade at all. At the genus level, Nannocharax as a group is reported as an egg-scatterer typical of small African stream characins, but captive breeding within the genus is explicitly described in the hobby literature as not established. Given the total absence of aquarium history for this particular species, no breeding mode, spawning trigger or parental-care pattern can be honestly reported here — this is a case where the correct answer is that the data is sparse, not that a mode should be assumed.
In the aquarium
Nannocharax hastatus is not a species anyone can currently buy or keep: it has no established presence in the aquarium trade, no hobbyist care reports, and was described from scientific collections rather than aquarium imports. Anything written about tank size, water parameters or tankmates for this specific species would be invented rather than documented, so this account does not attempt it.
What can be said is drawn from the genus rather than the species: Nannocharax as a group are diminutive, peaceable, bottom-oriented fish suited in principle to nano setups with sand or fine gravel, current, and cover from rocks or driftwood mimicking their swift-flowing rocky-stream habitat — but that describes the genus's general profile, not a verified care regime for N. hastatus, which remains essentially a museum-and-literature species rather than a hobby fish.
Conservation
Nannocharax hastatus has not been evaluated by the IUCN Red List and currently carries a status of Not Evaluated. This is unsurprising for a species described as recently as 2014 from a limited number of collecting localities in the Likouala drainage and the Momboyo river basin of the Republic of Congo and the Democratic Republic of Congo — a common situation for small-bodied, recently described African characins that have not yet been the subject of a dedicated conservation assessment.
No population trend, threat data or trade pressure has been documented for this species. Its narrow known range within the northwestern Congo basin means that, as with many recently described stream fish in the region, any future assessment would need dedicated fieldwork rather than existing records, and this account makes no claim about its conservation status beyond that formal Not Evaluated designation.