Taxonomy & naming
Phenacogrammus concolor was formally described by Melanie L. J. Stiassny, S. Elizabeth Alter, Joseph Monsembula Iyaba, and Tobie Liyandja in 2021 in a paper treating two new Phenacogrammus species from the Ndzaa River drainage published in American Museum Novitates (no. 3980). The type locality is a shallow, pool-like expansion of the Ndzaa River approximately 16 mi upstream of its confluence with the Mfimi River, Mai-Ndombe Province, DRC; specimens were collected during the dry season in July 2018. Eschmeyer's Catalog of Fishes is the governing authority for the valid name.
The genus Phenacogrammus belongs to the family Alestidae — the African characids — which radiate through sub-Saharan freshwaters. Within Phenacogrammus, P. concolor is distinguished from congeners by its diagnostic meristic combination (9–10 dorsal soft rays, 18–19 anal soft rays, 31–33 vertebrae) together with the striking absence of prominent black pigmentation on the flanks and caudal peduncle that typifies related species such as P. flexus. No subspecies or synonyms are recognised.
Morphology
Phenacogrammus concolor reaches a maximum recorded size of approximately 1.5 in (1.5 in) standard length, placing it among the smaller members of its genus. The body form follows the typical Phenacogrammus pattern: moderately laterally compressed, with a relatively deep mid-body profile and the forked tail characteristic of the family. Fin counts of 9–10 dorsal soft rays and 18–19 anal soft rays, together with a vertebral count of 31–33, separate it metristically from its nearest relatives.
The defining morphological feature — and the origin of the species' name — is the absence of conspicuous black pigmentation along the flanks and across the caudal peduncle. Where congeners such as P. flexus carry a well-defined dark lateral stripe or peduncle blotch, P. concolor presents a more uniform, unstriped coloration. No published data on live coloration in the aquarium exists at this time, and detailed colour descriptions beyond the diagnostic absence of black patterning are not available from the original description.
Habitat
The Ndzaa River, the only known locality for Phenacogrammus concolor, is a tributary of the Mfimi River within the broader Congo River basin of the Democratic Republic of Congo, situated in Mai-Ndombe Province. Type specimens were taken from a shallow, pool-like widening of the river approximately 16 mi upstream of the Ndzaa–Mfimi confluence during the dry season of July 2018. The original description characterises the collecting site as a clear-water stream set within riparian forest and open grassland or savannah.
No water-chemistry data (temperature, pH, conductivity) were recorded at the type locality or reported in the original description. As a Congo-basin alestid collected from clear lowland forest streams, P. concolor likely experiences the warm, soft, slightly acidic to neutral conditions typical of much of the Congo drainage, but this cannot be confirmed from published sources. The species is considered benthopelagic and freshwater obligate.
Feeding
No dietary data for Phenacogrammus concolor have been published. By analogy with the wider genus and family Alestidae, it is probable that the species is an opportunistic omnivore taking small invertebrates, insect larvae, and organic detritus — the feeding guild occupied by most small Congo-basin characids in similar microhabitats.
In the aquarium, were the species ever available in the trade, the feeding approach appropriate for related Phenacogrammus species would likely apply: good-quality small flake and micro-pellets supplemented with frozen or live foods such as Daphnia, micro-worm, and finely chopped invertebrates. Any specific dietary requirements remain undocumented.
Mating
No reproductive or behavioural data have been published for Phenacogrammus concolor. By comparison with other members of the genus and with alestid characids generally, the species is likely an egg-scattering, open spawner that deposits adhesive or semi-adhesive eggs among fine-leaved aquatic vegetation or submerged debris, with no parental care from either sex.
Sexual dimorphism, courtship behaviour, and spawning triggers are undescribed for this species at present. The original description does not comment on sex-specific differences, and no aquarium breeding records are known.
Breeding
No breeding data are available for Phenacogrammus concolor in either the wild or captivity. The species was described only in 2021 and has not, to current knowledge, entered the aquarium trade in any significant quantity.
Given family-level parallels, alestid egg-scatterers of similar size typically deposit small clutches of adhesive eggs over plant matter, with eggs hatching within a few days at tropical temperatures and fry requiring small planktonic foods. These generalisations should not be treated as confirmed facts for this species; all breeding details remain to be documented.
In the aquarium
Phenacogrammus concolor is not currently established in the aquarium hobby. As a species described in 2021 from a single locality in the DRC and absent from major hobbyist databases such as Seriously Fish, it has not been exported, bred, or kept in any documented capacity at the time of writing.
If the species were to become available, the general care framework for small Phenacogrammus would be a reasonable starting point: a well-oxygenated tropical tank with soft to moderately hard, neutral to slightly acidic water, a planted interior offering cover, and a peaceful community free of large or aggressive tankmates. At under 2 in standard length it would suit a modest aquarium. All husbandry parameters remain speculative until the species is studied in captivity.
Conservation
Phenacogrammus concolor has not been assessed by the IUCN Red List. As a species described in 2021 from a single collecting event at one locality in the DRC, no formal conservation evaluation has been conducted, and its population size, range extent, and threat status are unknown.
The Ndzaa River drainage, like much of the western Congo basin, is subject to ongoing pressures including habitat conversion, artisanal mining, and deforestation within its riparian catchment. A species known from a single locality — a shallow river pool in Mai-Ndombe Province — is inherently vulnerable to localised disturbance, but the absence of survey data makes it impossible to characterise this risk quantitatively. Further fieldwork is needed to establish whether the Ndzaa River population represents the full extent of the species' range or whether P. concolor occurs elsewhere in the Mfimi system.