Taxonomy & naming
Neolebias trewavasae was described by the Belgian ichthyologists Max Poll and Jacques Gosse in 1963. It sits in the genus Neolebias, a group of small West and Central African characins within the family Distichodontidae — the same family that contains the far larger, plant-grazing Distichodus and the deep-bodied citharinid grazers, though Neolebias itself never approaches their bulk. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the reference point for the genus's valid species; Neolebias trewavasae is recognised as a distinct, valid species within it, and no alternative combination is in current use.
The species epithet honours Ethelwynn Trewavas, the British ichthyologist renowned for her work on African freshwater fishes, particularly the cichlids of the East African lakes. In the trade it is occasionally sold as the African emperor tetra, a name that plays up its status as one of the largest and most colourful members of a genus otherwise made up of very small, plain-bodied fish.
Morphology
Neolebias trewavasae is a slender, small-finned characin and, notably, one of the largest species within its own genus — which says more about how small most Neolebias are than about this fish being large in absolute terms. Reported adult sizes cluster around 1.5–2 in total length, with FishBase recording a maximum standard length of roughly 1.5 in for males and unsexed individuals; some hobby sources note typical adult size closer to 1.5 in, with 2 in as an upper bound.
Colouration is understated rather than showy: the body carries the streamlined, laterally compressed profile typical of small stream characins, without the deep body or oversized dentition of its larger Distichodontidae relatives. Males are reported to flush a deeper red during spawning, which is the species' most distinctive colour feature and the likely inspiration for its "emperor" trade name.
Habitat
Neolebias trewavasae is native to West Africa, with sources pointing to the Guinea Forest region and specifically to Cameroon as a focal point of its distribution. It inhabits swift, shallow forest streams and associated waters typical of the region rather than large river channels, a habitat pattern shared by several small-bodied Neolebias species that favour clear, well-oxygenated running water over still backwaters.
Water across its native range is warm and on the soft, mildly acidic-to-neutral side: hobby sources report a temperature range of roughly 73–84 °F and pH 5.9–7.2. This sits within the broader pattern for African forest-stream characins — warm, soft-to-moderate water rather than the extreme blackwater conditions associated with some South American characins — and keepers should follow these figures rather than assume more acidic or more mineral-rich conditions.
Feeding
Neolebias trewavasae is reported as a carnivorous-to-omnivorous micropredator, taking small aquatic invertebrates in the wild — mosquito larvae, flies and other insect larvae make up the documented natural diet. This fits the pattern of small forest-stream characins that pick off drifting or surface insect prey rather than grazing on plant material, in contrast to the strongly herbivorous Distichodus within the same family.
In the aquarium this translates into a straightforward feeding regime built around small live and frozen foods — daphnia, brine shrimp, bloodworm and similar fare — supplemented with high-quality flake or micro-pellet. Given its small mouth, food size matters more than variety; oversized foods will simply go untouched by a fish barely 1.5–2 in long.
Mating
Neolebias trewavasae is described as an active, sociable species that shoals and holds loose territories within the group, with males reported to develop deeper red colouration as they approach spawning condition — the clearest external cue to breeding readiness available from current sources. Beyond that colour shift, detailed courtship behaviour for this particular species is not well documented in the sources consulted.
As with many small Neolebias, sexes are broadly similar in shape outside of the spawning-related colour change in males; data on additional sexual dimorphism is sparse and this account does not go beyond what the cache supports.
Breeding
Neolebias trewavasae is reported as oviparous and, per available hobby-aquaculture notes, a species where females scatter a modest clutch — cited at roughly 50 to 60 eggs — onto vegetation or rock surfaces rather than building any kind of nest. This matches the broader pattern for Distichodontidae: Distichodus and the citharinid grazers in the same family are egg-scatterers with no parental care, and Neolebias trewavasae appears to follow the same mode at a much smaller scale. Eggs are reported to hatch in around a week, with fry initially feeding on plankton-sized foods.
The species is rarely available in the aquarium trade and is not commonly bred by hobbyists; sources describe it as an infrequently kept and infrequently spawned fish rather than an established aquarium-breeding project, so keepers attempting it should expect to work from general small-characin egg-scatterer technique — dense fine-leaved plants or spawning mops, soft acidic water and immediate removal of adults, which are not above eating their own eggs — rather than a well-documented species-specific protocol.
In the aquarium
Neolebias trewavasae is a small, peaceful, active shoaling fish that should be kept in a group in a modestly sized planted aquarium — nothing like the tank footprint demanded by its much larger Distichodontidae relatives such as Distichodus, which can outgrow home aquaria entirely. Given its adult size of only 1.5–2 in, a group of these fish is comfortable in a nano-to-small community setup, provided tankmates are equally small and non-aggressive; sources note the species is territorial toward its own kind within the group even while remaining sociable and shoaling.
Water should be kept warm and on the soft, mildly acidic-to-neutral side — roughly 73–84 °F and pH 5.9–7.2 — with the swift, well-oxygenated flow of its native forest streams reflected in reasonable filtration turnover. It is rarely offered for sale, so keepers who do find it should treat it as a specialist acquisition rather than an easy pet-shop purchase, and should not expect the plant damage or aggression associated with its bigger family relatives — this is a quiet, undemanding fish rather than a destructive one.
Conservation
Neolebias trewavasae is assessed by the IUCN Red List as Least Concern, consistent with a small, range-restricted West African forest-stream species that is not reported to face significant documented pressure. As with many small, obscure single-region characins, detailed population trend data is limited, and the Least Concern rating should be read as reflecting an absence of known major threats rather than a well-studied, actively monitored population.
The species is rarely seen in the aquarium trade, which limits any pressure from wild collection for the hobby; broader habitat concerns for West African Guinea Forest freshwater systems — including deforestation and associated stream degradation — are relevant long-term watch items for the region's small endemic fishes generally, though no species-specific conservation concern is documented for Neolebias trewavasae in the sources reviewed.