Here's my profile of the species; it has some special requirements.
Kryptopterus vitreolus
Family: Siluridae
Common Names: Glass Catfish, Ghost Catfish
Origin and Habitat: River drainages in peninsular and southeastern Thailand. Found in gently-flowing streams and rivers having still water pools or margins; the fish rests in still water and stalks prey in gentle currents. Ng & Kottelat (2013) believe this species has a fairly small distribution range. All aquarium fish are wild caught.
Compatibility/Temperament: Peaceful; will eat small fry. Absolutely must be kept in a group of 5-6 or more, with non-aggressive tankmates that are not boisterous.
Diet: It preys on insect larvae and small crustaceans mid-water, not on the substrate like most catfish. Live and frozen artemia (brine shrimp), bloodworms, daphnia; will usually take prepared foods provided they drift in the gentle current.
Size: Attains 8 cm (3+ inches) in aquaria.
Minimum Tank Suggestion: 36 inches.
Water Parameters: Soft to medium hard (< 10 dGH), acidic (pH < 7) water, temperature 21-26C/70-79F.
Discussion
This very unique and interesting catfish must be kept in a group of at least 5 or 6; otherwise it may refuse to eat. It also cannot have boisterous tankmates for the same reason. A thickly-planted aquarium providing some swimming space with a gentle current is essential to calm this very timid fish. Floating plants will significantly assist in keeping this fish less stressed.
No external gender differences; females are rounder. The few reports of spawning in aquaria have had no details. The fish is allegedly bred commercially in SE Asia, perhaps with hormone injections, but most reliable resources question this. Wild-caught fish are likely the norm.
The common names Glass or Ghost Catfish are certainly apt for this fish, as the skeleton and swim bladder are clearly seen. The species lacks body pigment, and is scaleless. As noted under Diet, this fish swims mid-water unlike most catfish. This is a shy and rather nervous fish, quite sensitive to water parameters and highly susceptible to changes in water parameters or conditions. Being scaleless, any medications must be carefully used, and should never include salt.
The exact species of the aquarium Glass Catfish, popular in the hobby since at least 1934, was initially thought to be Kryptopterus bicirrhis, described by Valenciennes in 1840; but this very similar species, which grows about three times as large but otherwise has similar requirements, is very rare in the hobby. In 1989, T.R. Roberts described a new species, assumed to be the aquarium fish, as Kryptopterus minor. This has now been determined to be yet another similar species to the aquarium fish.
The confusion has now been resolved in a study by Ng & Kottelat (2013) that determined the aquarium fish to be a unique and new species which they named Kryptopterus vitreolus. The name of the genus, erected by P.Bleeker in 1857, comes from the Greek kryptos [= hidden] and pteryx [= fin], a reference to the reduced or absent dorsal fin of species in this genus. The species epithet vitreolus is Latin and means "of glass."
The Siluridae is one of 38 families within the order Siluriformes, the name from the Greek silouros [a fish species] and the Latin forma [shape]. The order is commonly known as the catfish. The family name Siluridae is from the Latin silurus, a type of river fish, probably the sheat-fish. The Siluridae holds a hundred living species in 12 genera, all freshwater fish though one European species may enter brackish water. They are distributed over Europe and southern and southeast Asia. The dorsal fin is absent in several species, but when present has less than seven rays; in the subject species the dorsal has one ray. Pelvic fins are small or absent, but the anal fin base is very long with 41 to 110 rays. There are one or two barbels on the lower jaw. [source: Fishbase]
References:
Ng, H-H, and M. Kottelat (2013), "After eighty years of misidentification, a name for the glass catfish (Teleostei: Siluridae)," in Zootaxa 3630(2), pages 308-316.
