Taxonomy & naming
Ailia coila was described by Francis Buchanan-Hamilton in 1822 from the Ganges river system. It is placed in the family Schilbeidae, a group of small to medium African and Asian catfishes that includes several semi-transparent, elongated species collectively called glass catfishes or sheatfishes in the hobby. The Catalog of Fishes (Eschmeyer, CAS) recognises Ailia as the valid genus; the species has at times been placed under older combination names in the genera Silurus and Pimelodus, but Ailia coila is the current accepted binomial.
The genus Ailia is small and distinctly Asian, occurring across the Indian subcontinent and into South-East Asia. The epithet coila derives from a local Bengali or Hindi vernacular name. The family Schilbeidae was long thought to be confined to Africa, but molecular work has confirmed the Asian schilbeids as a separate lineage sharing ancestry with them; their taxonomy has been revised several times and future shuffles remain possible.
Morphology
Ailia coila has the slender, elongated, laterally compressed body typical of Asian schilbeids. The skin is scaleless and semi-transparent, giving juveniles in particular a glassy, greenish-silver appearance through which the body cavity is partially visible. The head is flattened, with a wide mouth equipped with small teeth and several pairs of barbels used to locate food in low-light conditions.
Adult size is typically 3–4.5 in standard length. Like most schilbeids it lacks a visible lateral-line canal to any great degree and has a low, short dorsal fin. The caudal fin is forked. Small pectoral and dorsal spines are present but are not particularly strong or enlarged, and are not venomous — handling with dry hands is fine, though a container is preferred to a net since the barbels can tangle.
Habitat
Ailia coila is native to the Ganges and Brahmaputra river systems of India and Bangladesh, a large and complex drainage covering the north Indian plains and the Bengal delta. Within this system it inhabits large lowland rivers, backwaters, and floodplain habitats, preferring areas with moderate current and silty or sandy substrates where it forages at low light levels.
Water conditions in the Ganges and Brahmaputra are warm and soft to neutral — temperatures typically 72–82 °F and pH ranging roughly 6.5–7.5, with low to moderate hardness. These are productive, turbid river systems rather than clear blackwater, and the species is not a soft-acidic specialist in the sense of an Amazonian catfish. Like most lowland South Asian river fish it tolerates moderate variation in water chemistry.
Feeding
Ailia coila is a nocturnal benthic omnivore, foraging close to the bottom and in the water column after dark for small aquatic invertebrates, insect larvae, detritus, and presumably small crustaceans. In the wild the turbid, productive waters of the Ganges plains supply a rich invertebrate benthos.
In the aquarium it will accept sinking pellets, frozen bloodworm, brine shrimp, and other small prepared foods. Because it is primarily nocturnal, food should be offered after lights-out to ensure it is not out-competed by daytime-active tankmates. Small live or frozen invertebrates are a useful supplement.
Mating
No documented account of mating behaviour in Ailia coila exists in the aquarium literature, and spawning has not been reported in captivity. In this respect it resembles most other Asian schilbeids, including the better-known glass catfishes of the genus Kryptopterus, which are essentially not bred in home aquaria.
Based on the biology of related schilbeids, natural spawning is likely associated with the monsoon flood season in the Ganges–Brahmaputra lowlands, when rising water temperatures and swollen floodplains trigger reproductive activity — a common pattern in South Asian riverine species. The sexes are not obviously distinguishable externally.
Breeding
Ailia coila has not been bred in captivity to any documented degree. This places it with most other members of the Schilbeidae — the family does not produce the commercial aquaculture volumes seen in Pangasiidae or Clariidae, and English-language hobby literature records no successful home-aquarium spawning.
Aquarists keeping this species should not expect breeding to occur in a typical home tank. Stimulating spawning would likely require replicating monsoon cues (a drop in barometric pressure, a large cool water change to simulate rainfall dilution, and a sudden temperature fluctuation), but no reliable protocol has been established. For the time being, this is a species acquired for its appearance and behaviour rather than as a breeding project.
In the aquarium
Ailia coila is a rare import and an unusual choice, best suited to a species tank or a quiet community of similarly-sized, non-aggressive South Asian riverine fish. At 3–4.5 in as an adult it is a manageable size, but the tank should still be adequately sized — a minimum of 31.5 in length — with low to moderate flow, a sandy or fine-gravel substrate, and subdued lighting or floating plants to replicate the shaded lowland river environment.
The single most important care point is its scaleless skin: like all naked-skinned catfishes, Ailia coila is sensitive to copper-based medications and many organophosphate or chemical treatments that scaled fish tolerate. Always use conservative, half-dose treatments or catfish-safe alternatives; remove it to a hospital tank before treating a display with copper. Move this fish in a container rather than a net, as the barbels and spines can snag in mesh. It is primarily nocturnal, so provide caves, driftwood, or dense planting for daytime cover, and feed after lights-out.
Because it is rarely imported, husbandry data in the English-language hobby is sparse. Maintain clean, warm water (72–82 °F, pH 6.5–7.5, soft to neutral hardness) and keep it with peaceful, similarly-sized tankmates. It is unlikely to bother fish it cannot swallow.
Conservation
Ailia coila has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). It inhabits the Ganges and Brahmaputra drainage systems — among the most heavily populated and ecologically stressed river systems in the world — where pressures including large-scale water extraction for agriculture, dam construction, sedimentation from deforestation, and pollution affect a wide range of freshwater fish.
The species is not a target of large-scale commercial fisheries or the aquarium trade at any significant volume, and its small size means it is rarely recorded in systematic surveys. Data on its abundance and trend are sparse. Given the trajectory of habitat degradation in the Ganges plains, obscure small catfishes in this drainage are plausible candidates for reassessment as survey coverage improves.