Taxonomy & naming
Kryptopterus bicirrhis was described by the French zoologist Achille Valenciennes in 1840, originally placed under the name Silurus bicirrhis. It has also appeared in the literature as Cryptopterus amboinensis, reflecting older genus concepts before the family Siluridae was better understood. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Kryptopterus bicirrhis as the valid combination; the genus Kryptopterus currently holds around fifteen to twenty species of glass and related silurid catfishes from South and Southeast Asia.
The genus name Kryptopterus derives from the Greek kryptos (hidden) and pteron (fin or wing), alluding to the greatly reduced or absent dorsal fin — in most species of the genus the dorsal fin is reduced to a single small spine or is entirely absent. The specific epithet bicirrhis is Latin for 'two-bearded', naming the two long maxillary barbels that give the fish a graceful, whiskered look in the water.
Morphology
The glass catfish has a strongly laterally compressed, almost knife-like body that is very nearly fully transparent. The internal skeleton, swim bladder and organs are visible through the skin; the effect is striking under aquarium lighting. The skin is completely scaleless (naked), which is important for medication. There is no meaningful dorsal fin — it is vestigial — and the fish's entire outline is defined by an extremely long anal fin running almost the full length of the belly, a forked tail, and two exceptionally long maxillary barbels that project forward ahead of the snout.
Maximum recorded size is 6 in standard length (SL) per FishBase; this is a genuine adult size, not a rarely reached maximum — the species is routinely sold as small juveniles of 1–2 in. There are no locking dorsal or pectoral spines of the type found in armoured catfishes, though the pectoral spines, where present, can still catch a net; move the fish in a container to be safe. The sexes are not reliably distinguished externally in aquarium fish.
Habitat
Kryptopterus bicirrhis occurs across the Mekong and Chao Phraya river basins, the Malay Peninsula, Sumatra and Borneo. It inhabits slow-moving to still lowland rivers, floodplain lakes, and canal-like waterways, typically in areas of dense aquatic or overhanging vegetation that provides structure in otherwise open water.
Water conditions across its range are warm tropical, with FishBase recording a temperature range of 70–79 °F. The species favours slightly acidic to neutral water (pH roughly 6.5–7.0) of soft to moderate hardness. It is a lowland species, not a fast-water or hill-stream fish; it naturally holds station in midwater in loose shoals, facing into a gentle current, which is a behaviour it will reproduce in the aquarium if given sufficient companions.
Feeding
Glass catfish are midwater micro-predators. In the wild their diet includes pelagic insects, small fishes, aquatic worms, small crustaceans and other invertebrates; FishBase records hemipterans (water bugs) as a component of the natural diet alongside worms and small fish. In the wild the species targets small, mobile prey in open water rather than foraging on the bottom.
In the aquarium it strongly prefers live and frozen foods — bloodworm, daphnia, small brine shrimp and similar items are taken readily. Fine dry foods such as micro-pellets can be accepted by settled specimens, but many individuals remain reluctant or refuse dried food entirely. Because glass catfish are shy and easily out-competed, it is worth feeding at dusk or after lights-out in a community setting to ensure they receive enough. They will not compete with larger or more aggressive feeders.
Mating
Wild mating and spawning of Kryptopterus bicirrhis is associated with the onset of the rainy season, when rising water levels, reduced temperature and an abundance of food likely act as triggers. No detailed field observation of natural spawning behaviour has been published for this species.
In captivity there are no documented cases of successful natural spawning by hobbyists. Scientific accounts note that some closely related silurid glass catfishes have been spawned under controlled or hormone-induced laboratory conditions, but no repeatable technique for home breeding of K. bicirrhis has been established. Sexing is unreliable from external examination, which further complicates any attempt at captive breeding.
Breeding
Kryptopterus bicirrhis has essentially never been bred in home aquaria. The entire hobby supply is wild-caught, and the species should be regarded as not captive-bred for practical purposes. Aquarium breeder sources confirm that zero reliable home spawns have been recorded, and even hormone-induced spawning has been achieved only by scientists, not replicated as a hobbyist technique.
The conditions thought to be required — a simulated monsoon onset, abundant live food, falling temperature followed by warming, and possibly group spawning cues — are difficult to reproduce accurately at home. Keepers wishing to attempt breeding should be aware that the species' wild-caught status puts collection pressure on natural populations; sustainable sourcing from reputable dealers is advisable.
In the aquarium
Glass catfish are rewarding but demanding. A minimum group of six is essential: solitary or paired fish become stressed, lose colour (which in a transparent fish means they appear increasingly pale and dull), and often waste away. A tank of at least 25 US gal is advisable for a proper group at adult size (to 6 in SL); although juveniles are small, they grow and the group needs space to school freely in midwater.
The entirely scaleless skin makes this species significantly more sensitive than scaled fish to copper-based medications and to many other treatments. Dose at half the standard rate at most, or avoid copper entirely; use scaleless-fish-safe alternatives where possible. This sensitivity is shared with loaches, puffers and other naked-skinned fish. Water quality must be stable and mature — the species does poorly in new tanks or with fluctuating parameters; target pH 6.5–7.0, hardness around 8–10 dGH, and temperature 70–79 °F, changing no more than a degree or two at once.
Glass catfish are peaceful and should be kept with equally calm, non-competitive tankmates. Avoid robust or nippy fish that will bully them or steal food. Provide patches of dense planting and some open midwater swimming space; a gentle, steady current replicating their river habitat encourages natural shoaling behaviour. Diet should emphasise live and frozen foods; dry food acceptance varies and should not be assumed.
Conservation
The IUCN Red List assessed Kryptopterus bicirrhis as Least Concern in 2019. Its range is broad, spanning major river systems across Southeast Asia including the Mekong and Chao Phraya basins and island systems on the Malay Peninsula, Sumatra and Borneo, and it is not currently considered threatened at the range-wide scale.
Habitat alteration — including river damming, floodplain drainage and agricultural run-off — is an ongoing pressure across much of Southeast Asia, and the aquarium trade relies entirely on wild-caught fish since the species is not captive-bred. Responsible sourcing from suppliers that use sustainable collection practices is encouraged. Collection pressure on any single river population could be significant given the absence of a captive-breeding supply.