Acanthocobitis zonalternans

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Matt Clarke looks at a pretty loach called Acanthocobitis zonalternans, which although one of Thailand's most widespread loaches, is rarely seen for sale.

Scientific name: Acanthocobitis zonalternans (Blyth, 1860)

Origin: This is a widespread loach species. Museum data shows that the fish has been collected from Myanmar, India and Thailand in a number of major river systems including the Brahmaputra, Salween, Tapi, Mae Klong and Irrawaddy.

Size: There's some dispute, but somewhere between 4 and 8cm. These fish were juveniles measuring just 3cm in length and the pattern differs a little from that of the adults, which have a horizontal line of broken spots, rather than the almost solid longitudinal stripe seen in these fish.

Diet: Typical small loach fare: detritus, bloodworms, daphnia and other insect larvae, as well as sinking prepared foods.

Water: Found over a wide area so likely to be tolerant of a range of conditions. FishBase reports a pH of 6.8-7.8; GH 8-18C and a temperature of 24-26C.

Aquarium: The species lives among rocks and pebbles in riffles in clear streams and rivers. It is typically found in shallow water of just 5-50cm deep. It appears to be a relatively peaceful species that mixes well with other community fish species. It's best kept in a river-style aquarium furnished with lots of cobble like stones and larger rocks and heavily filtered with extra pumps for additional water movement.

Breeding: This species was bred recently by Manchester-based fishkeeper Andy Rushworth, probably for the first time.

Notes: This Indo-Chinese nemacheiline loach is one of four fish in the Acanthocobitis genus, the others are A. urophthalmus, A. rubidipinnis and the most common species, A. botia.

Identification: According to Kottelat's revision of the nemacheilines, A. zonalternans should have 13-15 soft dorsal rays, eight soft anal fin rays, an incomplete lateral line reaching no further than the pelvics and a suborbital flap on the eye of the male. A. botia has a longer lateral line, no suborbital flap, and 14-17 soft dorsal rays. A. rubidipinnis has a red tail and a much finer pattern of diagonal squiggles. It has more dorsal rays (18-19) a complete lateral line and a suborbital flap on males.

Availability: This is reportedly one of the most common loach species in western Thailand, however, it's rarely seen for sale in the UK. These ones were photographed at Wildwoods Water Gardens in Middlesex during June 2006.

Price: Around a fiver.

This article was first published in the November 2006 issue of Practical Fishkeeping.