Taxonomy & naming
Aphyosemion pseudoelegans was formally described by Sonnenberg and Van der Zee in 2012, published in Bonn Zoological Bulletin 61(1):3–12. The authors distinguished it from Aphyosemion elegans on the basis of dorsal fin colouration — almost entirely dark red to black in pseudoelegans rather than the red-dotted, lighter-backed pattern of elegans — an asymmetric caudal-fin design, and heavier flank pigmentation expressed as irregular narrow vertical bars rather than the confluent dot pattern of its congener. The genus and species both belong to the family Nothobranchiidae (the African killifishes), within the subgenus Aphyosemion sensu stricto and the elegans species group.
The species had been in the hobby before its formal description. The WAK reference library records a first import by Lambert in the 1960s from Boendé, DRC, and notes that later collections in 2002 by Van Deun near Boendé — along the road toward Yaa — provided the material on which the 2012 description is based. A second locality was found 22 mi from Boendé along the same road, within the Tshuapa River drainage. Paratypes run to 1.5 in SL for males and 1 in SL for females. Catalog of Fishes (Eschmeyer, Fricke & van der Laan) treats Aphyosemion pseudoelegans Sonnenberg & Van der Zee, 2012 as the valid name.
At several of its localities, including Ikela, the species is sympatric with its closest relative A. elegans, as well as with A. sp. aff. castaneum and at least one undescribed Aphyosemion. The co-occurrence of multiple Aphyosemion in the same stream system is a recurring feature of the Congo Basin's extraordinary killifish diversity.
Morphology
Males reach approximately 1.5 in standard length (FishBase), a size consistent with other small Aphyosemion from the Congo cuvette. Females are appreciably smaller — paratype females measured 1 in SL — and are plainer in colour, a pattern typical of the genus. Meristic counts are D 8–9, A 13–15, D/A overlap 8–10 scales, caudal fin ray count 24–28, and vertebral count 29–30, placing the species within the central cluster of the elegans group.
Male colouration is the species' diagnostic feature. The dorsal fin is almost completely suffused with dark red to black pigment — far denser and more uniform than in A. elegans — and the flanks carry irregular, narrow vertical red bars that differ from the more confluent, dot-like pattern of its sister species. The caudal fin shows an asymmetric extension pattern. The overall impression is a deeper-bodied, more heavily marked fish than A. elegans, which makes field separation straightforward once the difference is known. Females are drab olive-buff, useful for camouflage in leaf-litter-floored streams but of limited ornamental appeal.
Habitat
The native range of Aphyosemion pseudoelegans is restricted to the left-bank tributary system of the middle Congo River within the DRC, encompassing the Tshuapa, Momboyo, Lokoro, and lower Lomami drainages, as well as the Kasai drainage in Bandundu province. Known collection localities include Yayama, Boendé, Boteka, Lui Kotale, and the Losasa, Wele, and Lokoro rivers — all within the forest-covered interior lowlands of the cuvette centrale.
Habitat at the type locality consisted of extremely shallow, slow-moving water: the 2002 Van Deun collections found 29 specimens in water approximately 2–4 in deep, overlying a substrate of accumulated leaf litter 8 in or more deep, under closed-canopy forest cover. Such conditions are characteristically soft, acid, and tea-coloured from tannins leaching out of decomposing plant material. FishBase records the water as permanent or near-permanent — the species is non-annual and does not require seasonal desiccation, distinguishing it from the many annual Nothobranchius and Fundulopanchax that inhabit ephemeral savanna ponds across Africa.
The forest setting implies naturally low ambient light, high humidity, and stable water temperature year-round. Aquarium experience confirms the species tolerates temperatures around 81–82 °F, consistent with the warm, thermally buffered conditions of the Congo Basin interior forest.
Feeding
In the wild, Aphyosemion pseudoelegans almost certainly feeds as other small Aphyosemion of the elegans group do: as a generalist micro-predator of small invertebrates, insect larvae, worms, small crustaceans, and zooplankton found in the leaf litter and water column of forest streams. No detailed dietary studies specific to this species are available from the cache, but the shallow, leaf-litter-rich habitat strongly suggests ambush and sift feeding near the substrate, supplemented by surface-film insects.
In the aquarium the species accepts most standard small live and frozen foods: Daphnia, Artemia nauplii, blackworm (Lumbriculus), micro-pellets, and high-quality flake. As with many small Aphyosemion, live or frozen foods elicit the most vigorous feeding response and support the best colouration and spawning condition in males. Dried foods alone are often refused initially, particularly after transport stress.
Mating
Aphyosemion pseudoelegans is a non-annual killifish and a plant or mop spawner, as are all members of the elegans group. Rather than burying eggs in substrate to survive seasonal drought — the annual strategy of species like Nothobranchius — non-annual Aphyosemion deposit adhesive eggs onto fine-leaved plants, roots, filamentous algae, or artificial spawning mops, where the eggs incubate submerged in water without diapause. This approach is typical of species inhabiting permanent or near-permanent water bodies where the aquatic environment never completely dries out.
In the aquarium, males display to females with spread fins, the dark dorsal giving maximum contrast. Pairs or trios spawn over days or weeks rather than in a concentrated event: the male courts the female, they quiver alongside one another, and a single egg or small clutch is placed on the spawning substrate before the fish separate and resume normal activity. Eggs are small, round, and moderately adhesive. The WAK reference library considers breeding to be probably similar in style to A. elegans, which is a well-documented non-annual plant-spawner.
Breeding
Eggs of Aphyosemion pseudoelegans incubate in water at temperatures around 73–79 °F, hatching in approximately 10–14 days — a typical timeline for non-annual Congo Aphyosemion. The fry are very small at hatching and require appropriately sized first foods: infusoria or commercial fry powder for the first few days, followed by freshly hatched Artemia nauplii and microworms as the fry grow. Fishlore forum accounts for Aphyosemion in general report eggs as small and clear, hatching readily without the dried-peat conditioning required by annual species.
Because spawning is continuous rather than seasonal, a productive pair can yield small numbers of fry over extended periods. Breeders typically use floating acrylic-yarn spawning mops or fine-leaved plants such as Java moss; eggs can be harvested manually from the mop and incubated separately in shallow containers to prevent adult predation, or the adults can be transferred to a fresh tank and the mop left to hatch in situ. Growth to maturity is relatively slow compared to annual species but the fish are correspondingly longer-lived, with lifespans of two years or more under good conditions.
In the aquarium
Aphyosemion pseudoelegans is a specialist fish suited to experienced killifish keepers rather than general community aquarium setups. It is small — males under 1.5 in — and benefits from a densely planted, dimly lit aquarium that mimics the leaf-litter forest-floor aesthetic of its native streams. A species-only or genus-specific tank of 10–15 US gal is appropriate for a breeding pair or trio; adding too many males in a small tank leads to persistent pursuit of females and may suppress spawning.
Water parameters should reflect the soft, slightly acidic chemistry of the Congo forest: temperature 75–82 °F, pH 5.5–7.0, and very soft water (conductivity under 200 µS/cm) gives best results and the richest male colouration. Tannin supplementation via Indian almond leaves or peat filtration is beneficial. The tank should be tightly covered — Aphyosemion are accomplished jumpers and will exploit any gap.
Females are reportedly more difficult to maintain than males, a trait noted by FishBase. This is understood to relate to their sensitivity to water quality and temperature fluctuations. Regular small water changes with well-conditioned, soft water are more beneficial than occasional large changes. The species' restricted range, limited availability, and non-annual status mean it is seldom encountered in retail trade; it passes primarily through specialist killifish society networks and studbook programmes in Europe and North America.
Conservation
Aphyosemion pseudoelegans has not been evaluated by the IUCN Red List — it carries a status of Not Evaluated (NE) — despite being known from a small number of localities confined entirely to the rainforest lowlands of the Congo Basin interior in the DRC. Its dependence on shallow forest streams with intact closed-canopy cover makes it potentially sensitive to any deforestation or land-use change within the cuvette centrale, where logging, smallholder agriculture, and infrastructure development are increasing pressures.
The species has no buffer from habitat loss: it is a single-country endemic known primarily from the Tshuapa, Lokoro, and Lomami drainages. Unlike annual killifishes that deposit diapausing eggs able to survive temporary habitat loss, this non-annual plant-spawner requires continuous, permanent water and intact forest canopy. The population around Boendé — the type locality — is the best documented and has been accessed by collectors for decades, but no formal population surveys have been conducted.
The killifish-keeping community, particularly through the American Killifish Association and European equivalents, maintains living stocks of A. pseudoelegans in captivity and provides a de facto insurance population, but the number of individuals in hobby collections is small and genetically narrow. An IUCN assessment is warranted; given the restricted range, habitat specificity, and ongoing pressure on Congo Basin forests, a Vulnerable or Near Threatened listing would not be surprising once a formal evaluation is conducted.