Following Roberts (1997) G. ariza can be diagnosed by the following combination of characters: body with variably intense thin stripes dustributed mostly above the lateral line; larger individuals sometimes with a broad midlateral stripe; 32-35 lateral scales; 7-8/1/5-6 transverse scale rows; 8-9 branched dorsal-fin rays 8-9; 22-24+ 11-12=34(4), 35 (3) vertebrae; live colour pattern variable, overall dull dirty white to greyish, silvery or yellow.

This species is extremely widespread and has been recorded from Pakistan, Nepal, most of India, Bangladesh, Myanmar and southern China.

Type locality is ‘Bengal and western provinces, India’.

There is considerable confusion surrounding the identity of B. bagarius with its name having been widely applied to a relatively small species that is said to reach only 200 mm SL and considered to be common in northern India and much of Indochina.

This species is clearly unsuitable for the home aquarium given its eventual size and natural behaviour, and we know of only a handful of private aquarists with the facilities required to house it long-term.

The grouping currently contains four species but is in urgent need of review with a number of additional taxa thought to exist and B. yarrelli possibly representing a synonym of B. bagarius.

This species is also referred to as ‘giant’, ‘great’, ‘cobra’, or ‘Indian’ snakehead.

Although currently-considered to be distributed throughout much of southern Asia it is widely-accepted to represent a complex of related species in need of additional research.

A number of geographical variants exhibiting diffe…

It can be told apart from similar-looking congeners such as P. crescentus and P. muzaffarpurensis by the following combination of characters: barbels absent; lateral line incomplete with up to 5 pored scales; 20-22 lateral line scales; 8 predorsal scales; dorsal-fin with a vertically-orientated black streak and a black tip with orange markings; a dark spot at the base of the caudal peduncle.

This species is uncommon in the aquarium trade which is a little surprising given its huge natural range. Different populations can vary in colour pattern to an extent though all share the defining aspects given by Hamilton, comprising a diffuse yellow-golden marking on the operculum plus a dark spot on the caudal peduncle. The latter is usually surrounded by a variably-sized golden-yellow margin, and the dorsal-fin often contains irregular dark spots and streaks, these sometimes forming a longitudinal band.

This species is also referred to as ‘Asian knifefish’ or ‘ghost knifefish’ in the aquarium trade in the aquarium trade but arguably has no place in the ornamental hobby given its adult size and specialised requirements.

It is sometimes confused with the African species Xenomystus nigri but is easily told apart by its larger adult size and presence (vs. absence) of a dorsal fin.

Traded under various names including ‘mottled’, ‘eyepot’, ‘sand’ and ‘striped’ loach. It’s perhaps one of the better choices for those new to keeping nemacheilids being relatively hardy, peaceful and exhibiting some quirky behavioural traits. The characteristic ocellus, a dark marking at the top of the caudal peduncle that resembles an eye, is thought to have some function in predator distraction and is normally more intense in younger specimens.

This species’ name has been widely misapplied in the aquarium trade and hobbyist literature, most often in reference to the Southeast Asian species C. ornata, but unlike its relative is in fact very rarely exported for ornamental purposes although its is fished and cultured for food in India.

It can be told apart from C. ornata by possessing fe…