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Nemacheilus pallidus KOTTELAT, 1990


Order: Cypriniformes Family: Nemacheilidae


A relatively widespread species native to the Mae Klong and upper Chao Phraya river systems in Thailand plus the Mekong basin in Thailand, Laos, Cambodia and Vietnam, where it also occurs in the Dong Nai drainage. Type locality is ‘Huai Mae Phlung from Ban Pong (18°42’N, 99°58’E), to 17 kilometers upstream, Mae Nam Yom basin, Lampang Province, Thailand’.


Inhabits streams and small rivers with clear to turbid water, variable flow and substrates of mud, sand or small rocks. In the Nam river, Loei province, northeastern Thailand, it was collected from a shallow (~ 20 cm deep), moderately-flowing stretch with pebble substrate alongside Schistura nicholsi, Homaloptera smithi, Lepidocephalichthys hasselti, Acanthopsoides gracilis, Rasbora borapetensis and Amblyceps mangois. It was also recorded from a shallow backwater with sandy substrate and direct sunlight in the Siem Reap river, Cambodia.

Maximum Standard Length

55 – 60 mm.

Aquarium SizeTop ↑

An aquarium with a base measuring 60 ∗ 30 cm or more is recommended.


Not difficult to maintain under the correct conditions meaning we recommend designing the aquarium to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel and some large water-worn boulders. This can be further furnished with driftwood branches arranged to form a network of nooks, crannies and shaded spots. While the majority of aquatic plants will fail to thrive in such surroundings hardy genera such as MicrosorumBolbitis or Anubias spp. can be grown attached to the décor.

Like many fishes that naturally inhabit running waters it’s intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive. It also does best if there is a high level of dissolved oxygen and a decent level of water movement in the tank so external filters, powerheads, airstones, etc., should be employed in order to obtain the desired effect. As stable water conditions are obligatory for its well-being this fish should never be added to biologically-immature aquaria.

Water Conditions

Temperature23 – 26 °C

pH6.0 – 7.5

Hardness36 – 215 ppm


Nemacheilus species are omnivorous although the bulk of their diet consists of small insects, worms, crustaceans and other zooplankton with only relatively small amounts of plant matter consumed, mostly via the stomach contents of prey items.

In the aquarium they will accept dried foods of a suitable size but should not be fed these exclusively. Daily meals of small live and frozen fare such as DaphniaArtemiabloodworm, etc., will result in the best colouration and condition.

Behaviour and CompatibilityTop ↑

Fishes which inhabit similar biotopes in nature constitute the best options, especially  peaceful, open water-dwelling cyprinids since the presence of one or two schools can make a visible difference to the confidence of this naturally reclusive loach.

Other possibilities include balitorids like GastromyzonPseudogastromyzonBeaufortia, and Sewellia, plus Crossocheilus and Garra species. Some similarly-shaped relatives such as other NemacheilusAcanthocobitis, and Schistura spp. are excessively territorial or otherwise aggressive, although a combination may work in larger aquaria.

This species is peaceful with conspecifics and seems to appreciate being maintained in a group so the purchase of four or more specimens is highly recommended.

Sexual Dimorphism

Adult females are likely to be slightly larger and heavier-bodied than males. Mature males possess a suborbital flap with a pair of tubercules on the inner face and 6-10 rows of tubercules above and below the lateral line between the pelvic and anal fins. The first branched pectoral-fin ray is thickened with a few tubercules towards the tip, while there are 3-4 rows of tubercules on each branched pelvic-fin ray 2-6.



NotesTop ↑

N. pallidus can be distinguished from the majority of congeners by body patterning comprising 14-19 short, dark vertical bars on each flank, 13-16 saddle-like markings running along the dorsal surface, a dark spot on the caudal peduncle at the termination of the lateral line, and a dark blotch in the lower half of the first few dorsal-fin rays.

The similar-looking N. masyai is sometimes traded as N. pallidus, but the two can be told apart by body depth (14.8-19.1 % in N. pallidus vs. 12.6-17.6 % SL  in N. masyai), interorbital width (5.7-8.0 % vs. 4.9-6.8 % SL) and the fact that in N. pallidus the dark body bars and saddles are thinner than the light-coloured interspaces between (vs. wider in N. masyai).

Following Kottelat (1990) the genus Nemacheilus is characterised by a combination of characters as follows: elongate body; complete lateral line; presence of enlarged scales above and below the lateral line in some species; caudal-fin forked to deeply forked with enlarged upper lobe; large eye; small, strongly arched mouth; lips usually thin; usually no median interruption in upper lip; upper jaw with processus dentiformis (a tooth-like projection); no median notch in lower jaw; long barbels; males usually with suborbital flap, pectoral-fin rays 2-6 thickened and with rows of tubercules.

The family Nemacheilidae is widely-distributed across most of Eurasia with the Indian subcontinent, Southeast Asia and China representing particular centres of species diversity. It was first proposed as a genetically-distinct grouping in 2006, and according to current knowledge contains over 30 genera of which the most well-known in the aquarium hobby include AborichthysAcanthocobitisBarbatulaMesonoemacheilusNemacheilusPhysoschisturaSchistura, and Yunnanilus.

These were previously considered members of the family Balitoridae, subfamily Nemacheilinae, but phylogenetic studies have revealed that though closely related Balitorid and Nemacheilid loaches did not evolve from the same common ancestor and represent separate genetic lineages. The revised Balitoridae numbers over 30 genera including some popular aquarium subjects such as AnnamiaBeaufortiaGastromyzonHomalopteraLiniparhomalopteraPseudogastromyzonSewelliaSinogastromyzon, and Vanmanenia spp.


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    Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of Thailand, Burma, Laos, Cambodia and southern Viet Nam.
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    A generical classification of Nemacheilinae with description of two new genera (Teleostei: Cypriniformes: Cobitidae).
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    The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
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    Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes.
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    Comparison of evolutionary rates in the mitochondrial DNA cytochrome b gene and control region and their implications for phylogeny of the Cobitoidea (Teleostei: Cypriniformes).
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