Taxonomy & naming
Orthochromis gecki was described in 2018 by Frederic D. B. Schedel, Emmanuel Vreven, Bauchet Katemo Manda, Pacifique Kiwele Abwe, Auguste Chocha Manda and Ulrich K. Schliewen, in the journal Zootaxa, in a paper that simultaneously named five new rheophilic Orthochromis species from the upper Congo drainage of Zambia and the Democratic Republic of the Congo. The genus Orthochromis was erected by Greenwood in 1954 for small, current-loving haplochromine cichlids of African river rapids; the name combines Greek 'orthos' (straight) with 'chromis' (a cichlid), in reference to the nearly straight lateral profile of these stream fishes. As currently understood the genus is not a tight natural group but a convenient label for several lineages of rheophilic haplochromines scattered across the Malagarasi, Lufubu, Lake Tanganyika–region rivers and the upper Congo (Lualaba, Luapula and Lufira) systems. The describers placed gecki among the upper-Congo rheophilic Orthochromis and noted that, in their analyses, its meristic values overlap with those of the geographically distant Orthochromis indermauri of the Lufubu River, the two being distinguished by body shape and squamation. The specific epithet honours Jakob Geck, a German aquarist and long-serving volunteer in the ichthyology section of the Bavarian State Collection of Zoology (ZSM) in Munich.
Morphology
Orthochromis gecki is a small cichlid; the holotype measures 3 in standard length and FishBase gives a maximum of about 3 in SL. It has the typical rheophilic-Orthochromis build: an elongate, only moderately compressed body, a low and rather flat-headed profile, and reduced fins — the shape of a fish that spends its life pressed against rock in moving water rather than hovering in open water. The describers diagnose it within the genus partly by a relatively narrow interorbital width (roughly 9.6–12.9 percent of head length). Its most useful field character is the presence of true orange eggspots, or eggspot-like maculae, on the anal fin — a feature shared within the genus only with Orthochromis indermauri and Orthochromis torrenticola, and absent in most other Orthochromis. It is separated from Orthochromis torrenticola by having three rather than four anal-fin spines. Live colour is the muted brown-and-grey banding usual for stream haplochromines, with darker vertical bars on the flank; detailed notes on sexual dimorphism beyond the male anal-fin markings are limited in the original account.
Habitat
The species is known from the Lubudi River, a tributary of the Lualaba River — the headwater Congo — in the Democratic Republic of the Congo, with the type series taken downstream of the Kendo Rapids near Tshifuntshi village at roughly 10°34′S, 24°38′W in the Upper Lualaba ecoregion. This is genuine rheophilic habitat: the river there runs over a rocky bottom with patches of gravel and sand, is on the order of fifteen metres wide and only about half a metre deep at the collecting site, and is characterised by fast, well-oxygenated, broken water around rapids. Orthochromis are benthic fishes of exactly this setting, keeping low among stones in the current rather than ranging into still pools or lake margins. As with most of the upper-Congo rheophilic cichlids, the species' full range is poorly mapped and may be restricted to a limited stretch of the Lubudi and adjacent rapids.
Feeding
No dedicated dietary study has been published for Orthochromis gecki. By the ecology of the genus it is best understood as a benthic grazer-invertivore of fast water: rheophilic Orthochromis typically work the rocky substrate for aufwuchs — the film of algae and associated micro-invertebrates that coats stones in well-lit, oxygen-rich riffles — together with aquatic insect larvae and other small bottom invertebrates dislodged in the current. The low-slung body and subterminal mouth of these stream cichlids suit a life spent rasping and picking at rock surfaces. Any more precise account of its diet remains to be documented and would be inferred, not observed.
Mating
Courtship has not been described in detail for Orthochromis gecki, but rheophilic Orthochromis are maternal mouthbrooders, and the presence of orange eggspots on the male anal fin points squarely to the classic haplochromine spawning system. In that system a male occupies and defends a small territory among the rocks, displays to passing females, and leads a receptive female over a spawning site; the female takes the eggs into her mouth, and the eggspots on the male's anal fin are presented as decoys that prompt her to snap at them, drawing in milt to fertilise the clutch she already holds. In the turbulent, structured habitat these fish occupy, such territories are presumably anchored to particular rocks or crevices, but the specifics for gecki are inferred from the genus rather than recorded.
Breeding
There is no published account of spawning, clutch size or fry development specific to Orthochromis gecki. By the consistent biology of the rheophilic Orthochromis it is a maternal mouthbrooder: the female incubates the fertilised eggs and then the larvae in her buccal cavity for some weeks, releasing free-swimming fry that may continue to shelter in her mouth when threatened, with no paternal care. Clutches in small river haplochromines of this size are modest, on the order of a few dozen relatively large eggs, traded against the protection mouthbrooding affords in fast, predator-rich water. All of this is extrapolated from the genus; the actual brood size and developmental timing for gecki have not been documented.
In the aquarium
Orthochromis gecki is essentially unknown in the aquarium hobby. It is a recently described fish from a remote stretch of the upper Congo and is not part of the ornamental trade, so there is no established body of keeping or breeding experience for it; the rheophilic Orthochromis as a group are kept only by a handful of specialist enthusiasts.
Any husbandry notes are therefore extrapolated from its close relatives and its habitat. Rheophilic river cichlids of this kind need what their wild homes provide: clean, hard, alkaline, very well-oxygenated water kept in strong motion, a rocky and rubble substrate offering crevices and current-breaks, and stable warm temperatures. Powerheads or a river-tank manifold to generate brisk flow, scrupulous filtration and frequent water changes are the core requirements; soft, still, organically loaded water is the opposite of what they tolerate. They are small, busy, substrate-bound fish best kept in a species setup or with other robust rheophiles. The honest summary is that this is a fish for the dedicated rheophile cichlid keeper, not a general community fish, and one that for now is more likely to be read about than obtained.
Conservation
Orthochromis gecki has not been assessed by the IUCN Red List and carries no formal conservation status, consistent with its 2018 description. Its conservation interest follows from being, on present knowledge, a narrowly distributed endemic of a single upper-Lualaba river stretch and its rapids — the kind of restricted-range rheophile whose entire known population depends on a short reach of flowing water. The upper Congo / Katanga region faces real pressures from artisanal and industrial mining, sedimentation, deforestation and dam and weir construction, all of which can alter the flow, oxygenation and substrate that rheophilic cichlids require; rapids-dwelling fishes are especially vulnerable to anything that ponds or silts their habitat. No CITES listing or fishery interest applies, but the combination of a small range and a demanding fast-water niche makes the species a reasonable candidate for future attention as the region's freshwater fauna is more fully assessed.