Taxonomy & naming
Ompok miostoma was described by the French naturalist Léon Vaillant in 1902. It sits in the family Siluridae — the Old World sheatfishes and glass catfishes — within the genus Ompok Lacepède, 1803, which spans South and Southeast Asia. The genus Callichrous Hamilton, 1822, once used for several of these fish, is now treated as a junior synonym of Ompok, so older literature referencing this species or its relatives under Callichrous (or occasionally lumped with Wallago) reflects that pre-revision taxonomy rather than a distinct lineage. The Catalog of Fishes treats Ompok miostoma as the current valid name and combination.
The genus name Ompok is derived from a local Southeast Asian vernacular name for these catfishes rather than a classical root. The species epithet miostoma draws on Greek meion ("smaller" or "less") combined with stoma ("mouth"), a fitting descriptor within a genus whose species are distinguished partly by relative mouth and gape proportions. Because the genus has been repeatedly revised, and because several similar-looking Ompok circulate in the region, positive identification of trade fish sold simply as "Ompok" or "glass catfish" should not be assumed without expert confirmation.
Morphology
Ompok miostoma has the classic silurid sheatfish shape: a laterally compressed, elongated body, a long-based anal fin running most of the length of the underside, a short or absent dorsal fin, and a small adipose fin. The head is somewhat flattened with a terminal mouth and slender barbels used to feel out food in low light and murky water. Skin is entirely scaleless and smooth, as in all Siluridae — a trait that matters directly for medicating this fish (see "In the aquarium").
FishBase records a maximum size of 8.5 in standard length for this species, modest by the standards of the genus Ompok (which elsewhere includes species reaching well past 23.5 in) but still considerably larger than the slender juveniles sometimes seen in the aquarium trade under vague "glass catfish" or "sheatfish" labels. Like its relatives it likely carries fine, sharp fin rays rather than heavy locking spines, but as with all catfish it should be handled and netted with care rather than by hand.
Habitat
The species is native to the Mahakam River drainage of East Kalimantan, Borneo, a large blackwater-influenced river system that drains into the Makassar Strait. It is a freshwater, demersal fish, living and foraging near the bottom of river channels and connected floodplain habitats rather than in open midwater.
Older records reporting this species from Laos and Thailand are now attributed to misidentification of the related Wallago leerii, so the confirmed range of true Ompok miostoma is confined to Borneo. Specific water chemistry data (temperature, pH, hardness) for the Mahakam population were not available in the sources consulted for this profile; prospective keepers should treat the exact figures as data sparse and default to warm, well-oxygenated, softer tropical river conditions typical of Southeast Asian blackwater-adjacent systems rather than assume hard or alkaline water.
Feeding
FishBase places Ompok miostoma at a trophic level of roughly 3.8, consistent with a middle-to-upper-food-chain predator that takes other fish and aquatic invertebrates rather than grazing on plant or algal matter. Like other silurids it is most active around dusk and after dark, using its barbels to locate prey by touch and scent in low light or turbid water.
In the aquarium this translates to a predatory diet: sinking meaty foods such as prawn, whitebait, earthworm and quality carnivore pellets are appropriate, offered mainly in the evening. As with any predatory catfish, any tankmate small enough to be swallowed whole should be assumed to eventually become a meal.
Mating
No courtship or spawning behaviour specific to Ompok miostoma was documented in the sources available for this profile. Within Siluridae generally, glass catfishes (Kryptopterus) are essentially never bred in the home aquarium and the trade in them is wild-caught, while larger river sheatfishes such as Wallago and Silurus are river spawners whose reproduction in captivity, where achieved at all, is almost always managed at commercial or research-farm scale rather than by hobbyists.
One Indonesian aquaculture study (Balitbang/KKP) examined gonadal maturation in O. miostoma under controlled tank conditions, tracking hormones including cortisol, estradiol, vitellogenin and testosterone alongside glucose and haemoglobin as markers of reproductive readiness. This indicates active research interest in inducing spawning for aquaculture purposes, but it does not describe a natural courtship or pairing behaviour, and it does not represent an established hobbyist breeding method.
Breeding
Breeding of Ompok miostoma is not established in the home aquarium. The aquaculture research referenced above focused on monitoring reproductive hormone profiles in captive, controlled-tank populations — work aimed at understanding or eventually inducing spawning under farm conditions, likely with hormone assistance, rather than describing a natural spawning event that hobbyists could replicate.
Following the pattern seen across Siluridae, this species should be treated the same way as glass catfish and other river sheatfishes: essentially unbred in home tanks, with any commercial supply coming from wild collection or, at most, farm-scale production rather than aquarium spawning. Keepers should not expect to breed this fish and should assume any specimens in the trade are wild-caught or farmed rather than aquarium-bred.
In the aquarium
Ompok miostoma tops out at a modest 8.5 in SL for the genus, but that is still a substantial predatory catfish — far larger than the slender, translucent juveniles sometimes sold under generic "glass cat" or "sheatfish" labels, and well beyond what a small community tank can accommodate long-term. Anyone considering this species should plan for a large, long aquarium sized to a 20+ cm predatory catfish from the outset, not upgrade later.
Because it is scaleless, like all Siluridae, it is sensitive to copper-based medications and to some other treatments; dose conservatively and treat any disease outbreak with a plan appropriate for a naked-skinned fish. It is a nocturnal predator, so provide dim lighting, cover such as driftwood or overhangs for daytime retreat, and offer food after lights-out. Its diet is predatory — meaty foods only — and tankmates must be too large to be swallowed; small fish and shrimp will eventually disappear. Given the genus's history of misidentification and mislabelling in the trade, buyers should press for a confirmed species identification before purchase rather than assume a young "Ompok" or "glass catfish" will stay small.
Conservation
The IUCN Red List assesses Ompok miostoma as Near Threatened, based on the 2020 assessment (IUCN 2020.2). As a range-restricted endemic of the Mahakam River drainage on Borneo, its status is tied closely to the health of that single river system.
Borneo's rivers, including the Mahakam, face pressure from logging, oil-palm agriculture, mining, and associated sedimentation and water-quality decline, all of which can degrade demersal river habitat of the kind this species depends on. Because confirmed wild populations are confined to one drainage rather than spread across a broad range, localized habitat disturbance carries disproportionate weight for this species' long-term status.