Taxonomy & naming
Ompok eugeneiatus was described by the French zoologist Léon Vaillant in 1893, with a type locality in the Kapuas drainage of western Borneo, Indonesia. It has at times been placed in other genera during the long taxonomic churn of the sheatfish family, appearing in older literature under the combinations Callichrous eugeneiatus and Kryptopterus eugeneiatus; the Catalog of Fishes (Eschmeyer, California Academy of Sciences) and current authorities treat Ompok eugeneiatus as the valid combination.
The genus Ompok sits in the family Siluridae alongside Kryptopterus (the true glass catfishes) and the much larger Wallago and Silurus, a family distributed across Asia and, with Silurus, into Europe. Species-level identification within Ompok can be difficult and has historically relied on fin-ray counts and proportional measurements rather than obvious external markings, so aquarium imports are sometimes mislabelled among similar Ompok and Kryptopterus species.
Morphology
Like other silurids, Ompok eugeneiatus has a compressed, laterally flattened body, a long-based anal fin (58–62 soft rays, per FishBase), and a small, near-vestigial adipose fin or none at all. The head is small with a wide mouth carrying two pairs of barbels, and the eyes are proportionally large — an adaptation to a life spent foraging in low light. The skin is completely scaleless.
Maximum recorded size is 6.5 in, whether measured as standard length (Seriously Fish) or total length (FishBase) — modest by the standards of the sheatfish family, but still a fish that needs genuine open swimming space, not the cramped nano setups its slim, translucent-looking juveniles are sometimes sold for. As in all catfish, the naked skin means it is more sensitive than scaled fish to copper-based medications and should be dosed conservatively.
Habitat
Ompok eugeneiatus is native to Sumatra and Borneo, where it inhabits rivers and lowland streams, including watercourses running through or adjacent to peat-swamp forest. These are flowing, well-oxygenated waters, and the species is reported to require strong filtration and noticeable current in the aquarium to do well — a still, sluggish tank does not replicate its natural habitat.
Water chemistry across the sources is consistent: warm tropical conditions around 68–82 °F and a mildly acidic-to-neutral pH of 6.0–7.0, with soft-to-moderate hardness (roughly 3–10 °H). This is a soft, flowing-water fish rather than a still-water or hard-water species, and stable, clean, well-oxygenated conditions matter more for it than for many hardier catfish.
Feeding
Ompok eugeneiatus takes live, frozen and dried foods readily. As fish grow they can be offered larger meaty items such as chopped earthworm, prawn pieces and mussel alongside sinking pellets. It is not a fussy specialist feeder, but being shy and largely nocturnal in habit, it feeds most confidently after lights-out or when tankmates are not crowding the food.
Because of its size and predatory sheatfish lineage, any companion fish small enough to be swallowed whole should be regarded as potential food; feeding should account for a school of several fish competing for the same items rather than a single specimen.
Mating
Little is documented about courtship in this species specifically. ScotCat's factsheet notes that in the wild, females of this genus scatter their eggs over the substrate during river spawning tied to the rainy season, with no nest built and no pairing behaviour described — a pattern broadly consistent with river-spawning silurids rather than the guarded, cave- or bubble-nest strategies seen in some other catfish families.
Breeding
Breeding has not been achieved in the home aquarium (Seriously Fish is explicit on this point), and the trade in this species is essentially entirely wild-caught or, for the wider genus, dependent on river spawning cued to seasonal rains rather than any established captive protocol. This mirrors the pattern across the glass and sheatfish catfishes generally: the true glass catfish Kryptopterus is likewise not bred in captivity, and only the much larger river-spawning Ompok, Wallago and Silurus species are produced at any scale, and then almost exclusively on fish farms using hormone induction rather than natural aquarium spawning.
Aquarists should not expect to breed Ompok eugeneiatus at home. In the wild, fry that hatch from scattered eggs are free-swimming and require small live foods as they develop, but this stage is not something the hobbyist is likely to replicate or witness.
In the aquarium
This is a schooling fish and should never be kept singly or in pairs — a group of four or more is the minimum recommended, and ScotCat specifies a tank of at least 59 in (roughly 48 x 12 x 12 inches, about 30 US gal) to give a school adequate swimming room, with larger housing preferred as fish approach their 6.5 in maximum. Strong filtration and steady current are important, echoing the flowing rivers and streams it comes from; a still, low-flow tank is a poor match.
Ompok eugeneiatus is fairly peaceful but shy, and will consume any fish small enough to fit in its mouth, so tankmates should be medium-to-large, non-aggressive cyprinids, characins, or similarly sized Asian or South American catfish — ScotCat also lists larger cichlids as compatible. Provide shaded hiding places (driftwood, plant cover, dim lighting) since the species is retiring and mostly active at dusk and after dark. As with all scaleless catfish, dose copper and other sensitive medications conservatively, and move fish in a container rather than a net where possible — sheatfish teeth and fins can tangle and the handling stresses a shy, skittish species. This is a fish for experienced keepers who can commit to its space, current and water-quality needs, not a casual community addition.
Conservation
The IUCN Red List assesses Ompok eugeneiatus as Least Concern. It remains reasonably widespread across suitable lowland and peat-adjacent river habitat in Sumatra and Borneo, and is not currently considered at elevated risk.
As with many peat-swamp-associated Southeast Asian fishes, ongoing deforestation, peatland drainage and river degradation across Sumatra and Borneo are long-term pressures on the habitat this species depends on, even though the species itself is not presently flagged as threatened. The aquarium trade relies on wild-collected fish, since no captive-breeding programme exists for this species.