Taxonomy & naming
Chromidotilapia linkei was described in 1980 by the German ichthyologist and aquarium author Wolfgang Staeck, on material collected in southwestern Cameroon. The holotype (Senckenberg Museum, Frankfurt, register SMF 15107, with paratype SMF 15108) came from the Mungo River where the road between Kumba and Loum crosses it, at roughly 4°43′N — a clear, forested stretch of the coastal Cameroonian lowlands. The genus Chromidotilapia was erected by George Albert Boulenger in 1898 around the type species Chromidotilapia kingsleyae, and over the following century absorbed a scatter of names originally placed in Hemichromis, Pelmatochromis and Nanochromis before being given its modern shape. The Austrian ichthyologist Anton Lamboj's revisionary work from the late 1990s onward (which added Chromidotilapia elongata, Chromidotilapia mamonekenei, Chromidotilapia mrac, Chromidotilapia nana and Chromidotilapia melaniae) settled the genus at around eleven valid species, nine of them Central African. Within that group Chromidotilapia linkei belongs to the West-Central African assemblage rather than the wide-ranging Chromidotilapia guentheri lineage. Aquarium-trade taxonomy places it specifically in the informal batesii–finleyi species group alongside Chromidotilapia batesii, Chromidotilapia finleyi and an undescribed relative from the Korup region of Cameroon — a group of small, attractively coloured Chromidotilapia distinct from the larger-bodied guntheri–kingsleyae assemblage. It is most readily told from its congeners by its small adult size, the bright blue iris, the brown upper lip, and the very short first dorsal-fin spine (only about a third the length of the fifth). It sits in the subfamily Pseudocrenilabrinae, the African cichlid radiation, and carries no junior synonyms of its own.
Morphology
This is one of the smaller Chromidotilapia. FishBase records a maximum of 3 in standard length for male or unsexed fish from Staeck's type material, with an older total-length figure of about 3.5 in from the CLOFFA checklist — so even large adults are modest, palm-sized cichlids. The body is fusiform and only moderately deep, with a moderately convex dorsal head profile and a rounded caudal fin. The fin counts run to 15–16 dorsal spines and 10–11 soft rays, with three anal spines and seven anal soft rays, and there are 20–21 gill rakers on the first arch. The most useful field marks are the bright blue iris and the brown upper lip; juveniles, unlike those of some relatives, carry no black blaze in the front of the dorsal fin. The base coloration is an olive to greyish brown overlaid with subtle iridescence, and when the fish is stressed or sparring two continuous dark longitudinal bands appear along the flanks. Sexual dimorphism follows the genus pattern: males grow somewhat larger and longer-finned, while ripe females are rounder-bodied and, in breeding dress, develop the genus's hallmark reddish or pinkish-violet belly patch that signals readiness to a prospective mate. The differences are real but understated, and unsexed juveniles are difficult to tell apart. A distinctive, brightly coloured population from around Loum — the Cameroonian town the road to the type locality passes through — is traded and recognised among aquarists as the 'Loum' variant, one of several named colour races that crop up across the small-bodied batesii–finleyi group.
Habitat
Chromidotilapia linkei is a narrow-range endemic, known with confidence only from the Mungo and Wouri (Nkam-Wouri) river systems of southwestern Cameroon. These are short coastal drainages that rise in the Cameroonian highlands around Mount Cameroon and run down through evergreen rainforest to the Cameroon (Douala) estuary on the Gulf of Guinea, placing the species in the Northern Gulf of Guinea Drainages freshwater ecoregion. It is a benthopelagic fish of flowing, well-oxygenated forest streams and small rivers rather than still water. Contrary to a common assumption about Cameroonian forest cichlids, its water is not strongly acidic blackwater: FishBase gives a preferred range of pH 7.0–7.5 and soft-to-moderate hardness (from about 3 °dH upward) at tropical temperatures of 75–81 °F, and field hydrology for the Mungo itself records relatively high conductivity of 60–170 µS/cm with pH measured as high as 7.6–7.8. In other words this is a near-neutral to slightly alkaline, moderately mineralised stream fish of shaded, reed- and forest-lined channels. Published depth data are scant — like most small stream cichlids it occupies the shallow margins and bed of the watercourse, on the order of the first metre or two — and no in-situ depth band has been formally tabulated.
Feeding
Chromidotilapia linkei feeds mainly on detritus and aufwuchs — the film of algae, micro-invertebrates and organic particles that coats submerged surfaces in a forest stream. It is, in trophic terms, a benthic omnivore: FishBase places it around trophic level 3.3, reflecting a diet that mixes plant and detrital material with the small invertebrates entangled in it. Like its relatives it works the bottom and submerged wood and leaf litter, taking mouthfuls of substrate and sorting edible matter from sediment. The genus as a whole is built for this generalist micro-foraging rather than for predation on fish or large prey, and there is nothing to suggest Chromidotilapia linkei departs from that pattern. In its forest-stream community it functions as a small, unobtrusive grazer-detritivore of the streambed and the shaded shallows.
Mating
Chromidotilapia are among the most strongly pair-bonding of African cichlids, and Chromidotilapia linkei is no exception: it forms monogamous, mutually faithful pairs that jointly hold and defend a territory. Pair formation is mediated by the female's breeding signal — the reddish to violet belly patch she develops when ripe — which she displays to court a chosen male, reversing the usual cichlid script in which males do most of the soliciting. Once a bond is established the two fish cooperate closely, sharing territorial defence and, crucially, the care of the brood that follows. Aggression is directed outward at intruders and at rivals rather than between the partners, and a settled pair is comparatively peaceable toward each other, which is part of why pair-bonding Chromidotilapia have a reputation as engaging, watchable cichlids. The strength of the bond also means that arbitrarily pairing two adults rarely works as well as letting a compatible pair form from a group.
Breeding
Like the rest of the genus, Chromidotilapia linkei is a biparental, ovophilic (egg-loving) mouthbrooder — a relatively rare reproductive mode in which both parents take turns incubating the eggs and larvae in the mouth, rather than the single-sex mouthbrooding typical of the East African Rift lakes. The pair first cleans a spawning site, often inside or beside a cave or sheltered crevice; the female lays a comparatively small clutch — FishBase cites a maximum of about 150 eggs, and small-bodied congeners are similarly modest spawners — which the parents take up into the mouth shortly after fertilisation. The eggs and then the wriggling larvae are carried orally and passed between the two parents through the incubation period, and once the fry are free-swimming the pair continues to guard them as a tight school, the young darting back to the safety of a parent's mouth at any threat. This shared oral brooding, combined with the firm monogamous bond, makes the species a textbook example of cooperative biparental care. Precise figures for incubation time and release size in Chromidotilapia linkei have not been widely published, but they follow the well-documented genus pattern of a brood guarded for some weeks after release.
In the aquarium
Chromidotilapia linkei reaches the aquarium trade only occasionally and is far less often kept than its big cousin Chromidotilapia guentheri, but it is a rewarding subject for a keeper interested in West African pair-bonders. Its small size is an advantage: a single pair can be housed in a tank of around 35.5–47 in (roughly 55–65 US gal), which is modest by cichlid standards, though a longer footprint always helps when the fish are establishing a territory. The most important husbandry point is to respect the natural water chemistry, which is not the soft acidic blackwater many keepers reflexively associate with Cameroonian cichlids. In the wild this is a near-neutral to slightly alkaline, moderately mineralised stream fish; aim for pH around 7.0–7.5, soft to moderate hardness, and a temperature of 75–81 °F, with brisk filtration and good oxygenation to mirror its flowing-water home. A mature, well-filtered tank with stable parameters matters more than chasing extreme values.
Décor should provide structure and sightline breaks: smooth water-worn rock or wood arranged into caves and crevices gives a pair the spawning sites and refuges they need, and a sand or fine-gravel substrate suits a fish that grubs over the bottom for detritus and aufwuchs. Subdued lighting, leaf litter and some shade-tolerant or floating plants reproduce the shaded forest-stream feel and help the fish settle and colour up. Feeding is straightforward — a varied diet of small frozen and live foods (bloodworm, daphnia, brine shrimp, small crustaceans) alongside a good-quality sinking flake or micro-pellet with some plant content keeps condition and breeding readiness high.
Temperament is the genus's selling point: outside of spawning these are relatively peaceful, watchable cichlids, and a settled pair is far less belligerent than most substrate-spawning cichlids of comparable size. The proven route to a pair is to grow on a small group of juveniles and let a bond form naturally, then remove or rehome surplus fish, since forced pairings and crowded adults are the usual cause of trouble. Suitable tankmates are peaceful, similarly sized West African community fish — small barbs, characins, and robust surface-dwellers — kept clear of the pair's territory when they are in breeding mode. The species is uncommon enough that obtaining unrelated stock for breeding can itself be the hardest part of keeping it.
Conservation
The IUCN Red List assesses Chromidotilapia linkei as Endangered (EN), under criteria B1ab(iii)+2ab(iii), in an assessment by T. Moelants dated 16 February 2009; the population trend is recorded as unknown. The listing reflects the species' very small known range — restricted to the Mungo and Wouri systems of southwestern Cameroon — combined with a continuing decline in the quality of its forest-stream habitat. The coastal Cameroonian drainages at the foot of Mount Cameroon are under sustained pressure from deforestation, agricultural expansion (including oil-palm and plantation development), siltation and pollution, all of which degrade the clear, shaded, flowing waters this cichlid depends on. It carries no CITES or CMS listing and is harmless to humans and of negligible fisheries value, so the threats are habitat-driven rather than from exploitation. As a narrow-range endemic of a biodiverse but heavily impacted ecoregion, Chromidotilapia linkei is a species whose long-term security rests squarely on the protection of the small river systems it occupies; sources documenting its biology in detail remain thin, and basic monitoring of its populations would materially improve the picture.