Taxonomy & naming
The eyespot krib was described by the German-British ichthyologist Albert Günther in 1872 as Hemichromis subocellatus, in his report on collections recently acquired by the British Museum, from material taken in Gabon. The original series comprises three syntypes in the Natural History Museum, London (BMNH 1872.1.27.14-15, two specimens, plus an uncatalogued skeleton). For much of the twentieth century the fish was carried in the catch-all West-African genus Pelmatochromis, and older aquarium literature still lists it as Pelmatochromis subocellatus or even as a subspecies of the common krib (Pelmatochromis pulcher subocellatus). The modern genus Pelvicachromis was erected by the Belgian ichthyologist Dirk Thys van den Audenaerde in 1968, originally as a subgenus of Pelmatochromis, to gather the dichromatic dwarf 'kribs'; subsequent work by Anton Lamboj (2001, 2004, 2013), the foremost specialist on West-African cichlids, fixed Pelvicachromis subocellatus as the valid combination and clarified its place among its congeners. The genus sits in the African cichlid subfamily Pseudocrenilabrinae and is allied to the riverine genera Nanochromis and Chromidotilapia. The species is distinguished within Pelvicachromis by its comparatively deep, short body and by the faint, easily lost spotting on the upper caudal fin that gives the fish its name.
Morphology
This is a small, fusiform dwarf cichlid. The original measured material is modest: FishBase, following Lamboj, gives a maximum of about 2 in standard length, while aquarium accounts routinely report larger fish, with males to roughly 4 in and females around 3 in in total length. The discrepancy is partly a matter of how length is measured (standard length excludes the tail) and partly that well-fed captive fish outgrow the wild type series; Seriously Fish settles on about 3 in SL as a working maximum. The body is relatively deep and short for the genus (body depth roughly 35-42 percent of standard length), with a fin count of 15-16 dorsal spines, 9 dorsal soft rays, 3 anal spines and 7-8 anal soft rays. Diagnostically, any mid-lateral band does not extend onto the caudal fin and the dorsal fin lacks a dark basal band; the ocellated spots on the soft dorsal and upper caudal-fin rays from which the epithet derives are variable and may be present or absent. Sexual dimorphism is pronounced and, as in all kribs, the female is the showier sex. Males are larger and plainer, with neutral grey-brown to olive bodies, pointed dorsal and anal fins, and blue-patterned finnage. Females are smaller and rounder, and in spawning condition transform: the belly flushes intense pink, purple, metallic green or blue framed by black flanks, the cheek and lower gill cover turn golden yellow, and a broad band of the dorsal fin lights up metallic yellow, gold or silver. The species is traded as several distinct geographic colour forms - 'Moanda', 'Moulondo' and 'Matadi' among them - which differ in the female's exact palette and should not be interbred.
Habitat
Pelvicachromis subocellatus is restricted to the coastal lowlands of West-Central Africa, ranging from around Libreville in Gabon south to the lower Congo River near Moanda (Democratic Republic of the Congo), through the small coastal basins and the lower reaches of larger systems such as the Ogooué (Ogowe), Kouilou-Niari, Noumbi and Chiloango. An old report from southeast Nigeria is regarded by FishBase as questionable and unconfirmed, so the well-documented range is essentially the Gabon-Congo coastal strip. It is a fish of quiet water - pools, slow streams, still backwaters and small lakes - typically over sand or mud carpeted with leaf litter and submerged wood, often among marginal vegetation that offers cover. The defining feature of its habitat is proximity to the sea: some of the streams it occupies carry brackish water, and the species is one of the genuinely salt-tolerant dwarf cichlids. Wild water is generally very soft and warm; in nature these fish are reported from water of less than 1 degree of general hardness, though they prove remarkably adaptable across a wide chemical range. FishBase summarizes the envelope as pH about 6.0-8.0, hardness 5-19 dH and temperatures of roughly 22-26 degrees Celsius. As a small shoreline-stream fish it lives in shallow water; no precise depth band has been published, so its depth range is best treated as the shallow margins it occupies rather than a measured figure.
Feeding
In the wild the eyespot krib is essentially a benthic micro-omnivore and detritivore, working the soft bottom of its pools and streams for small invertebrates and the organic material that collects among leaf litter and sediment. FishBase places it at a trophic level near 3.2, consistent with a diet weighted toward small animal prey rather than plant matter. Like many cichlids it takes mouthfuls of sand and fine substrate, sifting edible particles and expelling the rest, and it forages mainly in the lower and middle water layers. In the community of a coastal stream it is a small, unobtrusive bottom forager rather than a dominant predator. It is not a dietary specialist: in captivity it accepts a broad range of foods readily, which is part of why it adapts so well to aquarium life.
Mating
Pelvicachromis subocellatus forms monogamous pairs and, like the rest of its genus, reverses the usual cichlid courtship roles: it is the female who initiates and drives the display. Outside breeding the fish are peaceful and retiring, swimming the lower and middle layers; when a female ripens she becomes the aggressor of the pair, intensifying in colour and soliciting the larger male. Her signature display is striking - she bows her body into a U-shape with the belly thrust forward and presents her glowing pink-to-purple abdomen, flanked by black and topped by a reflective, lit-up dorsal fin, dancing in front of the male to entice him. The middle of her flanks darkens to deep pink with a black patch on each side. Once a pair commits, they jointly hold a territory around a chosen cave, with the male doing most of the perimeter defence. Pair compatibility is the central difficulty: an arbitrarily paired male and female may never bond, and a mismatched or harassed partner can be killed. The reliable route to a working pair is to raise a group of six or more young fish together and let pairs form on their own. The pair bond can also turn volatile after spawning, when a brooding female may suddenly attack her mate.
Breeding
The eyespot krib is a biparental cave spawner with substrate-brooding care. The pair selects or excavates a cave - a rock crevice, a hollow under wood, or in aquaria an upturned flowerpot - and digs shallow pits in the surrounding sand. The female retreats inside and lays the eggs, typically up to about 200, attached to the roof or wall of the chamber; the eggs are amber to yellowish, the conspicuous colouring common to cave-spawned eggs that are hidden from predators. She tends and fans the clutch inside the cave while the male patrols and defends the territory outside, so a female's disappearance for a few days is often the first sign a spawn has occurred. Eggs hatch in roughly two to three days, and the larvae become free-swimming after about seven to eight days (some accounts give up to around thirteen days from spawning to free-swimming, depending on temperature); between hatching and free-swimming the brood is shuttled among pits and caves. Once mobile, the fry are herded near the bottom in a tight school, guarded by both parents - the female leading, the male holding the borders. The young take brine-shrimp nauplii, microworm and fine powdered foods at first, and grazing detritus and algae as well; they reach 0.5 in in their first couple of weeks and show the genus's longitudinal stripe pattern by about a month. Leaving the fry with the parents for a few weeks is thought to help imprint normal brood-care behaviour, though many breeders pull them earlier to protect them from being eaten or caught in the aggression that can flare between the adults.
In the aquarium
Pelvicachromis subocellatus is a rewarding aquarium fish, suited to beginners and experienced keepers alike, though it is one of the less commonly offered kribs and is usually sold as a named locality form. A single pair is comfortable in a tank from about 23.5–31.5 in long (roughly 20–25 US gal), with 39.5 in preferred for long-term keeping or for more than one pair; extra footprint matters most for managing the territoriality that appears at breeding time.
The decor should prioritise cover and spawning sites. A fine sand or smooth fine-gravel substrate is important, as these fish excavate pits and sift the bottom; coarse gravel works against that behaviour. Provide a generous scatter of hiding places and potential caves - clay flowerpots (an upturned pot with a notch cut in the rim is the classic spawning cave), stacked stones, lava rock, roots and driftwood. Plants are not essential but are appreciated for the additional cover, and species that tolerate gentle flow and subdued lighting suit the tank well. Low to moderate lighting and a gentle current best mimic the slow, shaded streams the fish comes from.
Water chemistry is forgiving. Although wild fish live in very soft water and the species shows its best colour and breeding readiness in soft, slightly acidic conditions, it tolerates a wide range: a temperature of 22-26 degrees Celsius (toward 26-27 for breeding), pH about 5.5-7.5, and hardness anywhere from very soft up to around 19 dH. Its salt tolerance means a little marine salt is harmless and can suit fish from the brackish coastal forms, but it is not required. Stable, clean water and regular partial changes matter more than chasing exact numbers.
Diet is easy: the fish accepts most prepared foods but does best on a varied menu built around live and frozen items - bloodworm, Artemia, Daphnia, Mysis and mosquito larvae - rounded out with quality pellets, granules or flake. Good feeding brings out the female's courtship colours.
Temperament is the main thing to plan for. Outside breeding the fish is peaceful, shy and retiring, and makes a fine community resident with small, non-boisterous tankmates: small characins, barbs, danios, rasboras, Corydoras, gouramis, small loricariids, and dither schools that coax the krib out of hiding. Avoid large, vigorous or aggressive fish that will bully it. When a pair breeds they become territorial and will drive other fish from their corner, so a community tank needs enough room for a defended zone, or the pair is best given a tank of its own. The two classic mistakes are forcing an incompatible pair (grow out a group instead) and keeping breeders with bottom-dwelling catfish that prey on eggs and fry. Watch the pair after the fry become free-swimming, as a female can turn on her mate at that stage.
Conservation
The IUCN Red List assesses Pelvicachromis subocellatus as Least Concern (assessed 17 October 2019 by K. Diouf, published 2020). The species is not listed by CITES. It has a reasonably wide coastal range across Gabon, Congo and the lower Congo basin, no evidence of major population decline, and is harvested only modestly for the aquarium trade - it remains one of the scarcer kribs in the hobby rather than a heavily collected one. As with the wider West-Central African coastal lowlands, the long-term backdrop is habitat pressure from deforestation, agriculture, urban and coastal development and pollution near the populated river mouths and estuaries it favours; none of these is documented as a present, species-level threat to this fish, but they are the context against which its status should be read. Because several distinct geographic colour forms exist and are interbred in the trade, maintaining pure locality lines is the main conservation-minded concern for hobbyists keeping the species.