Taxonomy & naming
Paraneetroplus omonti was described by the French aquarist and cichlid specialist Robert Allgayer in 1988, in a paper in the Revue Française des Cichlidophiles that redescribed Regan's genus Paraneetroplus and erected omonti as a new species from the Río Tulijá of Chiapas, southern Mexico. The epithet honours Jean-Marie Omont, a French aquarist described as 'a traveler devoted to the cause of the cichlid family.' The fish sits at the centre of an unresolved taxonomic disagreement: Eschmeyer's Catalog of Fishes lists Paraneetroplus omonti as a valid species, whereas FishBase synonymises it with Paraneetroplus gibbiceps (Steindachner, 1864), the Teapa cichlid, so that under the FishBase scheme omonti has no independent existence. The species (or form) belongs to the elongate, flowing-water 'lotic' grade of Paraneetroplus confirmed by the molecular revisions of McMahan, Matamoros, Piller & Chakrabarty (2015, Zootaxa 3999) and Říčan, Piálek, Dragová & Novák (2016); those broad phylogenies did not settle the narrow omonti/gibbiceps question, which awaits a focused revision. This atlas follows the Catalog of Fishes in treating omonti as a nominal species while flagging the dispute.
Morphology
Paraneetroplus omonti is a medium-sized, elongate and laterally compressed cichlid of the streamlined riverine form, reported at roughly 6–8 in in length. The body is a light greenish to bluish silver, marked with a variable pattern of darker spots, blotches or a broken mid-lateral band; the snout is comparatively elongate and the lips somewhat fleshy, with the comb-like teeth typical of the genus's grazing habit. In the features that supposedly separate it from gibbiceps, the differences are subtle and have not been universally accepted, which is precisely why FishBase folds the two together. Sexual dimorphism follows the heroine pattern: males grow larger and develop a steeper forehead and modest nuchal swelling in old dominant fish, while ripe females are deeper-bellied and drop a visible ovipositor when spawning. As with most narrow-range Mexican cichlids the detailed morphological record is thin and rests largely on Allgayer's description and a small body of preserved material.
Habitat
Whether treated as a species or a population of gibbiceps, the fish occurs on the Atlantic (Gulf of Mexico) slope of southern Mexico in the upper Río Tulijá, part of the Grijalva–Usumacinta drainage in Chiapas. It is a fish of fast-flowing, well-oxygenated montane and foothill water over rock, the rheophilic habitat preferred across the genus. FishBase, treating the fish under gibbiceps, gives a preferred temperature band of roughly 73–79 °F; the Tulijá headwaters are clear, cool, mineral-rich highland streams. The Usumacinta is one of the most fish-rich and most heavily endemic drainages of Middle America and is recognised as its own Freshwater Ecoregion of the World. Quantitative in-situ chemistry and a published depth range specific to this fish are sparse; the figures here lean on the FishBase envelope for the gibbiceps complex and the general character of the Tulijá rather than a dedicated field-limnology study.
Feeding
As a member of the gibbiceps complex of Paraneetroplus, Paraneetroplus omonti is a bottom-working omnivore. FishBase gives the complex a trophic level near 3.3, reflecting a diet of algae and aufwuchs scraped from rock together with the small invertebrates that come with it. The genus's comb-like teeth and elongate, current-adapted body suit a fish that works hard surfaces in flowing water, grazing the algal turf and foraging the substrate. The mix of plant, detrital and small-animal food places it among the generalist bottom foragers of the Tulijá rather than among dedicated piscivores, and much of its wild intake is low-energy grazed material.
Mating
No courtship observations specific to omonti have been published, and given the taxonomic uncertainty its reproductive biology is best read off the gibbiceps complex and the genus as a whole. Like most large heroine cichlids it forms a monogamous pair that bonds and then jointly holds and defends a territory. Courtship runs through the familiar cichlid repertoire of lateral displays, fin-spreading, jaw-locking and substrate cleaning, with both sexes intensifying in colour and the female dropping her ovipositor as she ripens. In a flowing-water cichlid of this build a defensible hard surface in or beside the current typically anchors the pair's territory, and intraspecific aggression rises as the territory is claimed and held.
Breeding
Paraneetroplus omonti is, like its genus, a biparental substrate (open) spawner. The pair cleans a hard surface — a flat rock, a slab of wood, the wall of a crevice — 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; cichlids of this body size typically lay several hundred eggs. Both parents share the brood: the female fans and tends the eggs while the male patrols and defends the perimeter, and after hatching the wrigglers are moved to pre-dug pits before the free-swimming fry are shepherded as a tight school by both adults. Systematic captive-breeding accounts for omonti as such are essentially absent, both because the fish is rarely kept and because its very identity is disputed.
In the aquarium
Paraneetroplus omonti is very seldom kept, and what husbandry advice exists is effectively the advice for the gibbiceps complex: a fish for the experienced keeper of riverine cichlids rather than a beginner. A pair is best in a tank of at least 75 US gallons (roughly 75 US gal) with strong, well-oxygenated flow, kept toward the lower tropical range (about 73–79 °F) to suit a fish of cool highland streams.
Water should be near-neutral to mildly alkaline (about pH 7.0–8.0) and moderately hard, matching the mineral-rich Tulijá; like all cichlids of its size it is intolerant of accumulated dissolved waste, so generous filtration and large regular water changes are essential. A substrate of sand or fine gravel with plenty of smooth water-worn rock suits its bottom-grazing, rock-scraping habits, and rockwork that creates broken sightlines and defensible territories is the sensible furnishing; it will rearrange décor and uproot rooted plants. Because the fish grazes a great deal of aufwuchs, its diet should be built around quality vegetable- and spirulina-based prepared foods supplemented with frozen or live items in moderation.
Tankmates should be similarly sized, robust riverine cichlids and large, fast dither fish; small or slow fish will be outcompeted or harassed during spawning. As with its relatives, the proven approach to a compatible pair is to grow a group of juveniles together. In practice this is a connoisseur's fish, almost never seen in the general trade and of interest mainly to specialists in Mexican riverine cichlids and to those following the omonti/gibbiceps taxonomic question.
Conservation
Because Paraneetroplus omonti is treated by FishBase and the IUCN's working taxonomy as a synonym of Paraneetroplus gibbiceps, it has no independent IUCN Red List assessment — it is best regarded as Not Evaluated as a distinct species, with any conservation read-across coming from gibbiceps, which the Red List lists as Data Deficient (assessed 18 September 2018). It carries no CITES listing. The underlying conservation concern is the same as for the rest of the genus: a fish (or population) confined to the upper Tulijá in the Usumacinta system, a region whose lowland reaches face damming, pollution, deforestation in the catchment, water extraction and introduced species. A rheophilic highland grazer is additionally exposed to anything that alters flow or warms and silts its streams. The most pressing need, however, is taxonomic — a focused revision to settle whether omonti is a valid species at all, without which a meaningful conservation assessment cannot be made.