Taxonomy & naming
The Belgian-British ichthyologist George Albert Boulenger described the kribensis in 1901 as Pelmatochromis pulcher, in the Proceedings of the Zoological Society of London, illustrated on his Plate 4. The type series is seven syntypes (BMNH 1901.1.28.13-20) held at the Natural History Museum in London, collected at the junction of the Ethiop and Jamieson Rivers in the Niger Delta of southern Nigeria. For decades the fish circulated in the trade under a string of names, most famously "Pelmatochromis kribensis" — the source of the hobby name "kribensis," which has long outlived its scientific basis. In 1968 the Belgian ichthyologist Dirk Thys van den Audenaerde erected the modern genus Pelvicachromis, originally as a subgenus of Pelmatochromis, to gather the small, sexually dichromatic West-African cave-spawners apart from the larger Pelmatochromis proper; pulcher is its type species. Several names fall into synonymy, among them Pelmatochromis aureocephalus and Pelmatochromis camerunensis. One name has not settled: Pelvicachromis sacrimontis Paulo, 1977 (the "giant krib"), described from just east of the Niger Delta without a preserved type, is treated as a valid species by Anton Lamboj (2004) but regarded by others as a colour form or close relative of pulcher — a genuine open question in the genus. Pelvicachromis belongs to the African cichlid subfamily Pseudocrenilabrinae.
Morphology
Pelvicachromis pulcher is an elongate, moderately compressed dwarf cichlid. FishBase gives a maximum of about 4.5 in total length; in practice males grow to roughly 4–4.5 in while females stay smaller at about 3 in — though the female is the deeper-bodied and plumper of the two, and at a glance can look the larger fish. A dark mid-lateral stripe runs from the snout through the eye to the tail and onto the caudal fin, with yellow-and-black barring about the face and a dorsal-fin base heavily pigmented in dark grey to black. Live colour is where the species earns its names: the lower flanks flush reddish-pink to wine-purple, the unpaired fins are washed with orange, red, yellow and sometimes blue, and the dorsal and caudal fins frequently carry gold-ringed ocelli (eyespots). Fin counts are 14-17 dorsal spines with 8-10 soft rays and 3 anal spines with 6-8 soft rays, and the jaws bear four to five rows of small monocuspid teeth. Sexual dichromatism and dimorphism are both strong: males are larger, more streamlined, and develop drawn-out, pointed dorsal, caudal and anal fins, while the ripe female is rounder and flushes an intense cherry-red to purple belly in courtship — the single most reliable field mark for sex. Males come in two colour morphs, a red-bellied form (red from the mouth and operculum down through the belly) and a yellow-cheeked form (red belly but yellow opercula and lips), a polymorphism tied to alternative reproductive tactics.
Habitat
The species is native to the coastal lowlands of West and west-central Africa, recorded from eastern Benin through southern Nigeria — the Niger Delta and the Cross River basin — to western Cameroon (Ndonga); a record from Sierra Leone is unconfirmed. Its classic stronghold is the drainage of the Ethiope River in the Niger Delta, the source of the type material. This is a fish of still and slow-flowing shallow water, almost always tied to dense marginal and submerged vegetation in lowland streams, creeks and delta channels shaded by overhanging bankside growth over sand and fine gravel. Its delta home spans a remarkable chemical gradient: near the sea the water is hard, alkaline and slightly brackish, while the feeder streams inland run soft and acidic, and the lowest-lying blackwater channels are softer and more acidic still. The fish tolerates the whole envelope accordingly — FishBase records pH 5.0-8.0 and hardness 5-19 dH — and the IUCN assessment notes it persists even in brackish and temporarily anoxic conditions, a versatility that underlies its hardiness in captivity. Field temperatures sit around 75–79 °F, most localities soft and acidic at pH roughly 5.6-6.9. As a demersal shallow-water fish it occupies essentially the top metre or so of these vegetated margins rather than any deep channel.
Feeding
The kribensis is an opportunistic benthic omnivore that works the substrate and vegetation of its shallow habitat, with FishBase placing it around trophic level 3.3. Reported wild diets differ with locality and method: classic accounts describe it feeding on worms, small crustaceans and aquatic insects, while a study of fish from the Sombreiro River in Nigeria, cited by Anton Lamboj (2004), found gut contents dominated instead by diatoms, filamentous algae, higher-plant material and detritus. The honest reading is that pulcher takes whatever the leaf-litter and vegetated shallows offer — a mix of small invertebrates and plant-and-algal matter — rather than specialising. That dietary flexibility is part of why it adapts so readily to prepared foods in the aquarium, and ecologically it functions as a small generalist forager of the densely planted creek margins it inhabits.
Mating
Outside of breeding, kribs live in loose mixed aggregations of non-reproductive males and females. Reproduction reorganises this into a system of male-held territories built around shelter: in the wild, territorial males defend multi-purpose patches of roughly a quarter of a square metre centred on a hole beneath a leaf, stone or piece of wood (Sjölander 1972; Martin & Taborsky 1997). The two male colour morphs pursue different tactics — red-morph males are more aggressive and patrol their territories more intensively than yellow-morph males — a documented case of alternative male mating strategies in a cichlid. Pair formation is led largely by the female, who flushes her purple belly and dances before a chosen male to entice him. Established pairs are monogamous, and once a bond forms both partners share territory defence and the digging or clearing of a spawning cave. This female-driven courtship and the reversed dichromatism — the female being the brighter, signalling sex — make pulcher an unusually instructive species for watching cichlid pair behaviour unfold.
Breeding
Pelvicachromis pulcher is a biparental cave spawner (a substrate brooder), and its spawning is sequential and orderly. The pair select or excavate a cave — under a leaf, stone, root or, in aquaria, a flowerpot — and the female sticks the adhesive eggs in lines of about ten to the roof and walls of the chamber. Field and laboratory work by Martin & Taborsky (1997) put the wild-type clutch at roughly 40-80 eggs, while aquarium spawns are frequently larger, with hobby accounts of 50 to as many as 300 eggs. The partners take turns during spawning, only one fish in the cave at a time while the other guards the entrance. Care is then divided: the female broods and fans the eggs and wrigglers inside while the male defends the surrounding territory, with same-sex intruders driven off by the matching parent. The eggs hatch in about two to three days, and the fry become free-swimming roughly a week (seven to eight days) later, at which point both parents shepherd the shoal in the open, collecting strays in the mouth and even carrying and chewing food — plant fragments, snails, or prepared flake — to spit toward the young. One notable quirk, demonstrated experimentally by Reichard and colleagues (2013), is that water pH during early development skews the brood's sex ratio and male morph: more acidic conditions tend toward female-biased broods and more alkaline conditions toward male-biased ones — a form of environmental sex determination layered over the fish's genetics.
In the aquarium
The kribensis is, deservedly, a standard recommendation for a first cichlid and a first breeding project — small, hardy, colourful, and willing to spawn in a community tank with no special coaxing. Both sexes turn sharply territorial when guarding a brood, so plan for that.
Tank: a single pair fits in about 23.5–31.5 in of length (roughly 10–20 US gal), with more room wanted if other fish share the aquarium. The decisive detail is shelter — at least one cave is effectively mandatory, an upturned terracotta flowerpot with a notch chipped from the rim being the classic choice, alongside coconut shells, PVC offcuts, rockwork and driftwood. A substrate of sand or fine, smooth gravel suits the fish's habit of digging spawning pits and protects it from injury, and rooted or potted plants (weighted at the base) supply the dense cover it expects while breaking up sightlines.
Water: wild-caught kribs do best in soft, slightly acidic to neutral water mirroring their creek habitat — pH about 5.5-7.5 and temperatures of 75–81 °F — but the captive-bred stock that dominates the trade is notably more forgiving of harder, more alkaline conditions, sometimes to pH 8 and beyond. Would-be breeders should aim for the softer, more acidic end, where spawning is more readily triggered; because developmental pH skews the brood's sex ratio, a mid-range pH around 6.5-7.0 gives the most even mix of male and female fry. Keep filtration gentle, especially once fry are present — an air-driven sponge filter is ideal — and avoid strong current and harsh lighting, neither of which these shaded-creek fish appreciate. Feeding is trivial: the omnivore accepts quality cichlid pellets and flake readily, kept varied with live and frozen foods such as bloodworm, brine shrimp and small crustaceans for best colour and breeding condition.
Tankmates: kribs work well with peaceful upper- and mid-water schooling fish — tetras, rasboras, danios, barbs — and small West-African dwarf cichlids given room for separate territories, and schooling dither fish actually help by drawing a shy pair into the open.
Common mistakes: keeping them with slow, long-finned fish they may nip; adding bottom-dwellers such as catfish to a breeding tank, where they compete for cave space and may eat eggs or fry; an under-decorated tank that leaves a pair defending the whole aquarium; and — the cruellest — buying a random "pair" rather than growing on a group of six or more and letting a compatible bond form, since a mismatched pairing can end with one fish killing the other. Once a pair is established, expect it to spawn again and again, and watch the male during fry-rearing — if the young are removed too early he may harry an unready female hard.
Conservation
The IUCN Red List assesses Pelvicachromis pulcher as Least Concern (assessed 22 April 2019, published 2020, by Lalèyè, Moelants & Olaosebikan), citing a wide distribution across the coastal lowlands of Benin, Nigeria and Cameroon, tolerance of a broad range of conditions including brackish and low-oxygen water, and no major identified threats; the population trend is listed as unknown. It carries no CITES or CMS listing. The species is harvested for the international aquarium trade, but commercial supply is overwhelmingly captive-bred — the krib breeds so freely in captivity that farmed stock long ago displaced significant wild collection, which buffers wild populations from trade pressure. The broad backdrop for its native range is the heavily developed, oil-producing Niger Delta, where habitat degradation, pollution and hydrological change are real regional pressures; none is documented as a present danger to this particular, adaptable cichlid, but they form the context in which its long-term status should be read.