Taxonomy & naming
Chromidotilapia elongata was described by Anton Lamboj in 1999 in a paper devoted to the cichlid fauna of the Dimonika Biosphere Reserve in the Mayombe massif of the Republic of the Congo ("Zur Cichlidenfauna des Biosphärenreservats von Dimonika (Mayombe, Kongo), mit Beschreibung zweier neuer Chromidotilapia-Arten", Verhandlungen der Gesellschaft für Ichthyologie 1: 139–156). The species was one of two Chromidotilapia named new to science in that work, the other being Chromidotilapia mamonekenei. The type locality is given as the uppermost reaches of rivers and creeks in the vicinity of the village of Dimonika, within the Loémé basin — a small coastal drainage rising in the Mayombe forest. The genus Chromidotilapia itself was erected by George Albert Boulenger in 1898, and elongata is placed in it without controversy on the strength of its pair-bonding, biparental ovophilic mouthbrooding biology and its general anatomy. Within the chromidotilapiine assemblage — the West and Central African cichlid lineage that also includes Pelvicachromis, Benitochromis, Divandu and Pelmatochromis — Chromidotilapia is regarded as ancient and morphologically heterogeneous; later workers (Lamboj and colleagues, and the molecular phylogeny of Schwarzer and others) noted that variation in mouthbrooding behaviour and pigmentation across the genus hints at a more complex internal structure than the single name suggests. No junior synonyms are attached to Chromidotilapia elongata, and it has not been reassigned since its original description.
Morphology
True to its epithet, Chromidotilapia elongata is the slimmest member of its genus. Adults reach only about 3.5 in in standard length, making it a genuinely small cichlid, and Lamboj's diagnosis singles out body proportion as the decisive feature: specimens of 1.5 in SL or larger are notably gracile, with a body depth of just 28.3–35.1% of standard length (averaging about 31.7%), well below the deeper-bodied build of most congeners. The fin counts are typical for the genus — roughly 14 to 15 dorsal spines and 10 to 11 soft dorsal rays, with three anal spines and seven to nine soft anal rays. The first gill arch bears a moderate complement of 13 to 18 gill rakers. In coloration the species is comparatively plain: it lacks the large, well-defined flank spots seen in some relatives, and instead shows four to six vertical bands, or two longitudinal rows of dark blotches joined by short horizontal lines, a pattern that becomes most obvious when the fish is stressed or displaying. As in other Chromidotilapia, the sexes differ — males grow somewhat larger and more robust, while ripe, courting females develop a brighter, more contrasting belly and pelvic region, the visual signal that organizes pair formation in the genus.
Habitat
Chromidotilapia elongata is a narrow-range endemic, recorded with confidence only from the headwater streams and creeks around Dimonika in the Mayombe massif of the Republic of the Congo, in the small coastal Loémé drainage. These are upland rainforest brooks rather than large rivers: shaded, clear-to-tannin-stained waters running over forest-floor substrates. Surveys of the broader Mayombe stream network describe nutrient-poor brown waters in which high concentrations of humic acids drive the pH down, the classic soft, acidic blackwater chemistry of a Central African forest catchment. FishBase records a pH range of about 6.8 to 7.5 for the species and notes water temperatures from around 66 °F upward — distinctly cooler than the lowland habitats of many tropical cichlids, reflecting the elevation and dense canopy of the Mayombe highlands. The fish is benthopelagic, working the lower part of the water column and the stream bed. Its restriction to a single small basin in a single mountain range is the central fact of its ecology and the reason so little field data exist for it; it has never been documented from the larger Kouilou-Niari or Ogowe systems that drain the same region.
Feeding
No dedicated dietary study has been published for Chromidotilapia elongata, and its trophic ecology must be read from its anatomy, its genus and its habitat. FishBase places it at an estimated trophic level of about 3.3, the value typical of a small omnivore that takes a mixed diet of animal and plant material. Chromidotilapia as a genus are bottom-oriented foragers — the better-known Chromidotilapia guentheri is a sediment-sifter that takes mouthfuls of substrate and winnows out small invertebrates, insect larvae, crustaceans, worms, seeds and detritus, behaviour that has earned the genus the loose label of African eartheaters. In the leaf-littered, invertebrate-rich beds of its Mayombe forest streams, Chromidotilapia elongata is best understood as a micro-predator and omnivore of this kind, gleaning aquatic insect larvae and other small benthic invertebrates from among submerged litter and the stream bottom, supplemented by whatever plant and detrital material it processes along with them. Its modest size confines it to correspondingly small prey.
Mating
Chromidotilapia are among the most reliably monogamous of African cichlids, and Chromidotilapia elongata follows the genus pattern of stable, pair-bonded reproduction. Rather than a male holding a harem, a single male and female form a lasting bond and jointly hold and defend a territory through the breeding cycle. Pair formation is driven by mutual display, in which the female's brighter, contrastingly coloured belly is the key courtship signal — a reversal of the usual cichlid emphasis on male ornament, and a feature shared across the genus. Once bonded, the partners cooperate closely, a prerequisite for the shared brood care that follows. Because the species has so rarely been observed, the fine detail of its courtship has not been documented in print, but there is no indication that it departs from the well-described monogamous, biparental social system of its better-studied relatives, where the pair bond itself is the organizing unit of reproduction.
Breeding
Chromidotilapia elongata is a pair-bonding, ovophilic, biparental mouthbrooder — a reproductive mode that is one of the defining specializations of the genus and is comparatively unusual among cichlids worldwide. The pair spawns on a substrate in the manner of an open or cave spawner, but the eggs are then taken up into the mouth and incubated orally; uniquely in this lineage, both parents share the mouthbrooding duty, passing or dividing the developing clutch between them rather than leaving it to the female alone, and both continue to shelter the free-swimming fry in their mouths when danger threatens. No clutch count has been published specifically for Chromidotilapia elongata; congeneric Chromidotilapia typically produce small broods on the order of a few dozen to perhaps a hundred or more relatively large eggs, in keeping with the heavy parental investment that biparental mouthbrooding entails. The cool, soft, acidic forest-stream conditions of its native Mayombe brooks are presumed to be the natural spawning environment, but the species has not been the subject of a documented captive breeding account, so the precise incubation period, fry size at release and developmental timetable remain unrecorded for this particular fish.
In the aquarium
Chromidotilapia elongata is essentially an aquarium rarity: it has occasionally been maintained by specialists — including its describer, Anton Lamboj — but it is not a commercially traded fish and almost never appears in the general hobby. There is no established body of husbandry experience to draw on, so any keeping advice is extrapolated from the genus and from the species' natural environment, and should be treated as provisional.
What is clear is that this is a soft-water specialist of cool, acidic forest streams, and a tank for it should reproduce those conditions rather than generic tropical-cichlid parameters. Soft, well-filtered water with a pH on the acidic-to-neutral side of the genus range (roughly 6.0–7.0) suits it, and the temperature should be kept toward the lower end of the cichlid norm — the species tolerates conditions down to around 66 °F and does not need or want the high 20s that many African cichlids are given. Tannin-stained "blackwater" achieved with leaf litter, alder cones or peat filtration both mimics the wild habitat and helps buffer the water soft and acidic. A modest footprint is adequate for so small a fish, but the layout matters more than the volume: this is a shy stream cichlid that wants subdued lighting, a fine substrate, driftwood, roots and broken sightlines.
Because it is a monogamous pair-bonder, the natural unit to keep is a compatible male–female pair given a defensible territory; as with other Chromidotilapia, an unbonded or mismatched pair can turn aggressive in close quarters, so a planted, structured tank that lets a subordinate fish retreat is sensible. Feeding should reflect its omnivorous, invertebrate-leaning wild diet — small live and frozen foods such as bloodworm, daphnia and brine shrimp, alongside good-quality sinking prepared foods. Given its rarity, cool-water preference and exacting chemistry, Chromidotilapia elongata is a fish for the dedicated West African cichlid enthusiast rather than the general keeper.
Conservation
The IUCN Red List assesses Chromidotilapia elongata as Data Deficient, in an assessment by T. Moelants dated 16 February 2009. The category reflects exactly the problem the species presents: it is known from so few collections, in so small an area, that the data needed to judge its status simply do not exist. What is known is a cause for caution rather than alarm — the species appears to be a narrow-range endemic confined to the headwater streams of a single coastal basin in the Mayombe massif, the kind of restricted forest-stream specialist that is inherently vulnerable to localized habitat change. Its type locality lies within the Dimonika Biosphere Reserve, which affords its core range a degree of nominal protection. The broader pressures on Mayombe forest streams — deforestation, agriculture, and the degradation of the soft, humic, low-nutrient waters these fish depend on — are the relevant background threats, but none has been documented as acting specifically on this species. It carries no CITES listing. A proper field survey of the Loémé headwaters would be needed before its conservation status could be assessed with any confidence.