Taxonomy & naming
Congolapia louna was described in 2012 by Andreas R. Dunz, Emmanuel Vreven and Ulrich K. Schliewen in the journal Ichthyological Exploration of Freshwaters (volume 23, pages 155-179), in the same paper that erected the genus Congolapia itself. The genus was raised to hold three species: Tilapia bilineata Pellegrin, 1900 (designated the type species, now Congolapia bilineata), Tilapia crassa Stiassny & Schliewen (now Congolapia crassa), and the wholly new Congolapia louna. Congolapia was thus carved out of the old catch-all 'Tilapia', part of a wave of generic dismemberment that swept through the substrate-spawning tilapiine cichlids in the early 2010s as molecular phylogenetics exposed 'Tilapia' as a deeply paraphyletic assemblage; Dunz and Schliewen formalised that revision a year later in their 2013 reclassification of the haplotilapiines. The genus is diagnosed by a combination of morphological, colour and molecular characters, the most cited being a densely scaled caudal fin paired with spatulate (spoon-tipped) teeth in both jaws. Within the family it sits in the African subfamily Pseudocrenilabrinae, in the tribe Tilapiini in its now-restricted sense. The species is anchored by a small type series of five specimens; the holotype and paratypes derive from the Louna River collection, and the name is registered in ZooBank. No synonyms exist — it has been a valid species under a single name since the day it was described.
Morphology
Congolapia louna is a modest-sized, laterally compressed cichlid reaching about 6 in in standard length, the maximum recorded in the original description. The fin counts are typical of the genus: sixteen dorsal spines followed by ten or eleven soft rays, three anal spines and eight or nine soft rays. All body scales are cycloid, with twenty-six to twenty-seven scales along the horizontal line, eighteen to twenty-one in the upper lateral line and nine to ten in the lower. In life the background colour is a light olive-green to greyish, paling to whitish on the chest and belly; the lower half of the head is whitish to faintly yellow and the upper half a brownish olive, with white lips and a dark-brown iris. A yellowish lachrymal stripe runs from below the eye to the angle of the jaw, and there is a distinct black spot on the gill cover (opercular spot). Tellingly, the dorsal fin bears no 'tilapia mark' — the dark ocellus that many tilapiine cichlids carry on the soft dorsal — and the fins are otherwise plainly greyish, the pectoral-fin base lightly brownish. The species is told apart from its two congeners by hard characters rather than colour: it carries far more gill rakers on the first ceratobranchial (about thirteen, versus eight to eleven in Congolapia crassa and eight to ten in Congolapia bilineata), and differs from Congolapia bilineata in having two complete scale rows (plus a row of very small scales) between the upper lateral line and the base of the last dorsal spine, and a longer last dorsal spine (12.9-15.0% of standard length versus 9.4-13.2%). It is shallower-bodied than Congolapia crassa, with only minimal overlap. No sexual dimorphism has been described — the type series was too small and too incompletely studied to establish how, or whether, the sexes differ.
Habitat
Every known specimen of Congolapia louna comes from one place: the Louna River, a right-bank affluent of the Lefini River, which is itself a right-bank tributary of the Congo (Zaire) River in the Republic of the Congo. The Lefini drains the southern margin of the Bateke Plateau, a sandy upland of well-leached Kalahari sands east of Brazzaville, and its waters run clear and comparatively swift over pale sand — a strikingly different biotope from the tea-coloured, slow blackwaters of the central Congo's flooded forest. The original description records the type series as collected in fast-flowing water over a sandy bottom, which places the fish among the rheophilic (current-loving) elements of the Congo's tributary fauna rather than the still-water pool dwellers. No in-situ chemistry was published for the Louna with the description, but the wider middle-Congo and Bateke Plateau streams from which it comes are characteristically warm, soft and weakly acidic to near-neutral, draining nutrient-poor sands; aquarium guidance for the basin's fishes accordingly centres on roughly 24-28 degrees Celsius and a pH near 6.0-7.5. FishBase classifies the species as a freshwater, tropical fish; depth has never been formally measured, but as an inhabitant of a flowing sand-bottomed stream it is, in practice, a shallow-water fish of perhaps the upper metre or two of the channel. Its two congeners, Congolapia bilineata and Congolapia crassa, are by contrast widely distributed through the central Congo basin; louna alone is the basin micro-endemic of the trio.
Feeding
No gut contents have been published for Congolapia louna, so its diet is inferred rather than observed. The dental and gill-arch anatomy is informative, though. The genus is diagnosed in part by spatulate teeth in both jaws — broad, spoon-shaped tips of the kind tilapiine cichlids use to scrape, crop and dislodge attached material rather than to seize and hold prey. Coupled with the unusually high gill-raker count that sets louna apart from its congeners (about thirteen on the first ceratobranchial), this points to a fish that grazes and gleans from the substrate and works small particulate food from the water it passes over its rakers, in the broadly omnivorous, plant-and-detritus-leaning manner of the substrate-spawning tilapiines from which the genus was split. FishBase places its estimated trophic level near 3.2, the value of a generalist that takes both plant material and small invertebrates. In its fast, sandy stream it most plausibly functions as a benthic grazer-omnivore, mopping algae, biofilm, detritus and small bottom invertebrates from the sand and rock of the channel floor.
Mating
The courtship and pair-forming behaviour of Congolapia louna has never been observed — the species is known only from preserved museum material and has, as far as the literature records, never been kept alive. What can be said is drawn from its phylogenetic position. Congolapia belongs to the substrate-spawning tilapiine lineage, the group that retained the name 'Tilapia' after the genus was dismantled precisely because its members are nest-building, substrate-guarding cichlids rather than mouthbrooders. In that lineage, reconstructed on the most inclusive tilapiine phylogenies as the ancestral parental-care state, breeding pairs typically establish and jointly defend a territory on the bottom, clean a spawning surface or excavate a shallow pit, and form a comparatively durable monogamous bond through the brooding period. By extension, Congolapia louna is expected to be a territorial substrate spawner in which a male and female pair up over a defended patch of the streambed before spawning — but this is a genus-typical expectation, not a documented account of this species.
Breeding
Reproduction in Congolapia louna is undocumented; no spawning, clutch, egg or larva of the species has been described, and it has not been bred in captivity. The reproductive mode is therefore assigned from the genus and tribe: like the other substrate-spawning tilapiines from which Congolapia was separated, it is expected to be a biparental substrate spawner — depositing adhesive eggs on a cleaned surface or in a shallow nest and guarding and fanning them as a pair, rather than mouthbrooding. This is the well-supported ancestral and prevailing care system of the Tilapia-group cichlids (the substrate spawners that kept the 'Tilapia' name when the biparental and paternal mouthbrooders were split off as Sarotherodon and the maternal mouthbrooders as Oreochromis). No clutch size has been measured for any Congolapia; substrate-spawning tilapiine cichlids of comparable body size typically lay on the order of a few hundred to a couple of thousand eggs per spawning, so any figure cited for louna is a genus-typical estimate only. Both parents would be expected to guard the eggs and the resulting free-swimming fry. FishBase rates the species' resilience as high, with a minimum population-doubling time under fifteen months — a value derived from general life-history modelling rather than from observed broods.
In the aquarium
Congolapia louna is, for all practical purposes, not an aquarium fish. It has no presence in the ornamental trade, no hobbyist breeding record, and no published live photograph — the FishBase page still shows only a generic cichlid drawing in place of a portrait. Anyone who genuinely encountered it would be doing so as a field collector in the Republic of the Congo, not as a buyer at a shop. What follows is therefore extrapolation from the biotope and from experience with comparable Congo-basin tilapiines, offered honestly as such rather than as a husbandry record.
The fish comes from fast, clear water over sand, so the tank that would suit it is a flowing, well-oxygenated one: strong circulation from a powerhead or a generously sized canister return, a fine sand substrate it can sift and graze, and scattered water-worn rock or root for cover and sightline breaks. A 6 in substrate-spawning cichlid that defends a nest needs floor space rather than height; a footprint on the order of 47 in length (roughly 65–80 US gal) would be a sensible minimum for a pair, more if kept with others. Water should track the soft, warm, weakly acidic-to-neutral character of the Bateke Plateau streams — about 24-28 degrees Celsius and pH in the 6.0-7.5 band — kept clean with regular large water changes, since rheophilic stream fish are intolerant of accumulated dissolved waste. Diet would be the easy part: an omnivore's menu of quality sinking pellet and flake, frozen and live invertebrates (bloodworm, daphnia, brine shrimp) and a vegetable or algae component to suit its scraping dentition. The honest bottom line is that this is a wild-only, scientifically known fish; nothing about keeping it has been verified, and the notes above are a biotope-based best guess, not a proven recipe.
Conservation
Congolapia louna has not been evaluated by the IUCN — it carries no Red List assessment and is therefore formally Not Evaluated (NE), as both FishBase (Red List version 2025-2) and the Cichlid Room Companion record. A live search of the IUCN Red List returns no entry for the species. It is likewise unlisted by CITES and CMS, and is harmless to humans and of negligible fisheries value. The absence of an assessment should not be read as reassurance: the species is known from a single short stretch of one small river, on the strength of just five specimens collected for the original description, and nothing has been published on the size, trend or stability of its population. A range that narrow — a micro-endemic of the Louna within the Lefini system on the Bateke Plateau — is intrinsically vulnerable to any localised disturbance, whether sedimentation, deforestation, agricultural runoff or hydrological change in its headwater catchment. The broader Lefini basin lies partly within the Leconi-Bateke-Lefini conservation landscape, which affords its watershed some protection, but no protected-area coverage has been demonstrated for this fish specifically. Until the Louna is resurveyed and the species relocated and assessed, its true status remains genuinely unknown.