Taxonomy & naming
The Usumacinta cichlid was described by the French aquarist Robert Allgayer in 2002, originally as Theraps ufermanni; the epithet honours Andreas Uferman, associated with the German aquarium literature on these fish. The species spent its brief early history shuffled between Vieja and Theraps as those genera were variously circumscribed. The molecular revision of the herichthyine cichlids by McMahan, Matamoros, Piller & Chakrabarty (2015, Zootaxa 3999) erected the new genus Kihnichthys for ufermanni alone, naming it for P. Herman Kihn-Pineda of the Universidad de San Carlos de Guatemala, who has devoted a career to the fishes of Guatemala. The comprehensive phylogeny of Říčan, Piálek, Dragová & Novák (2016) supported the same arrangement. Kihnichthys is monotypic, and its closest relative is the genus Cincelichthys; the two represent the deep-bodied, still-water ('lentic') ecomorph of the Theraps-group radiation, in contrast to the slim flowing-water genera Theraps, Chuco, Rheoheros and Paraneetroplus. Whether Kihnichthys and Cincelichthys should ultimately be merged is noted as not yet fully resolved.
Morphology
Kihnichthys ufermanni is a moderately large, deep-bodied and laterally compressed cichlid built on the short, tall 'lentic' plan — the body form of a still-water fish rather than the streamlined shape of its current-dwelling relatives. FishBase gives a maximum of about 10 in standard length, making it a substantial fish. The ground colour is silvery to olive-grey, often with a greenish or bluish iridescent sheen and a variable pattern of broken vertical bars or mid-lateral blotches that strengthen with mood and breeding condition. Sexual dimorphism follows the heroine pattern: males grow larger, develop a steeper forehead and, in old dominant fish, a modest nuchal hump, while ripe females are deeper-bellied and drop a visible ovipositor when spawning. As a recently described, narrow-range species its detailed morphological record rests largely on Allgayer's description and a small body of subsequent material rather than systematic study of living fish.
Habitat
The species is restricted to a few rivers of the Usumacinta basin spanning Chiapas (Mexico) and Guatemala, on the Atlantic (Gulf of Mexico) slope. Its short, deep body and lentic ecomorphology mark it as a fish of the slower, deeper, more lake-like reaches — lower river valleys, side lagoons and backwaters — rather than the fast riffles its slim relatives favour. FishBase classes it as freshwater and benthopelagic and assigns it the tropical range; specific in-situ temperature and pH measurements for this species are sparse, but its relatives occupy warm, near-neutral to alkaline, moderately hard water, and the same envelope applies here. The Usumacinta is recognised as its own Freshwater Ecoregion of the World, noted for an exceptionally rich and partly endemic cichlid fauna, of which Kihnichthys ufermanni is one of the narrow-range endemics. Quantitative field limnology and a published depth range specific to this species are lacking; the figures here lean on the genus's ecomorphology and the general character of the basin rather than a dedicated study.
Feeding
FishBase assigns Kihnichthys ufermanni a trophic level near 3.3, estimated from its size and closest relatives rather than a published gut-content study. Its deep-bodied lentic relatives in Cincelichthys and Vieja are predominantly grazers and browsers of plant and detrital material, and the same generalist, bottom-oriented omnivory is the most likely habit here: working the substrate and hard surfaces for algae, aufwuchs, plant matter and the small invertebrates that come with them. As a still-water specialist it forages the soft-sediment and vegetated zones of the slower river reaches rather than scraping rock in fast current. The detailed diet of this recently described, seldom-studied fish remains to be documented in the field.
Mating
As with most large heroine cichlids, reproduction in Kihnichthys ufermanni is organised around a monogamous pair that bonds and then jointly holds and defends a territory. No courtship observations specific to this species have been published, so the account is built from the biology of its deep-bodied relatives. Pairs form within a group as fish mature; courtship runs through the familiar cichlid sequence of lateral displays, fin-spreading, jaw-locking and substrate cleaning, the female deepening in colour and dropping her ovipositor as she ripens. Intraspecific aggression rises as a pair claims and defends its patch, and the reliable route to a compatible pair in captivity is to grow a cohort together and let a bond form rather than to force two adults into proximity.
Breeding
Kihnichthys ufermanni is, like its relatives, a biparental substrate (open) spawner. The pair selects and meticulously cleans a hard surface — a flat rock, a broad leaf, a slab of wood, or the tank bottom — and the female lays an adhesive sheet of eggs over it while the male follows to fertilise. A precise wild clutch count has not been published for the species; large heroine cichlids of this body size typically lay on the order of several hundred adhesive eggs, and a productive pair can be expected to fall in that range. Both parents share the brood: the female fans and tends the eggs while the male patrols and defends the perimeter, and after the eggs hatch the wrigglers are moved to pre-dug pits before the free-swimming fry are shepherded as a tight school by both adults. The young feed initially on infusoria and fine prepared foods. Systematic captive-breeding accounts are essentially absent for this rarely kept, recently described species.
In the aquarium
Kihnichthys ufermanni is a fish for the experienced large-cichlid keeper rather than a beginner — a substantial, deep-bodied, territorial cichlid that needs real volume and management. A single adult or a pair is best in a tank of at least 75 US gallons (roughly 75 US gal), and a longer 100-gallon-plus footprint makes managing the fish, and any tankmates, considerably easier. Unlike the slim, current-loving Theraps and Chuco, this is a still-water fish, so it does not need the strong flow those species want; a stable, well-filtered tank with gentle-to-moderate circulation suits it.
Water should be warm and stable, around 77–84 °F, with a near-neutral to mildly alkaline pH (about 7.0–8.0) and moderate hardness; the fish is hardy across this range but, like all big cichlids, is intolerant of accumulated dissolved waste, so generous filtration and large regular water changes are essential. A substrate of sand or fine gravel suits its bottom-foraging habits; like its relatives it will rearrange décor and uproot rooted plants, so robust or potted plants, smooth water-worn rock and driftwood that create broken sightlines and defensible territories are the sensible furnishings. As a probable omnivore that takes a good deal of plant and detrital material, its diet is best built around quality vegetable- and spirulina-based prepared foods supplemented with frozen or live items in moderation.
Tankmates should be robust, similarly sized cichlids and large, fast dither fish; small or slow fish will be outcompeted or, during spawning, harassed. The species is territorial and becomes markedly more aggressive in breeding condition, so the proven approach is to grow a group of juveniles together to allow a natural pair to form and to spread aggression. It is a genuinely rare fish in the trade, of interest mainly to specialists in Mexican and Guatemalan cichlids.
Conservation
The IUCN Red List assesses Kihnichthys ufermanni as Data Deficient, in an assessment dated 28 November 2018. The Data Deficient listing reflects exactly what its biology suggests: a recently described fish restricted to a few rivers of the Usumacinta basin for which there is not enough information on population size, trend or specific threats to place it confidently in a threatened or non-threatened category. It carries no CITES listing. That narrow, few-river endemism is itself the heart of the conservation concern — a species confined to a small part of the Usumacinta system has little room to absorb local pressures, and the basin faces the familiar threats to Mexican and Guatemalan Atlantic-slope rivers: habitat alteration, pollution, deforestation in the catchment, water extraction and introduced species. None of these is documented as a population-level threat to this particular cichlid, but for a Data Deficient narrow-range endemic the appropriate posture is caution and a call for the basic distribution and population surveys the Red List flags as missing.