Taxonomy & naming
H. M. Smith described the species in 1931 from the Mekong River at Pang Chao, northern Thailand. It was described outside Opsarius and moved there later, so the authority is in parentheses. Opsarius is in the family Danionidae and holds a group of stream-dwelling fishes of southern and southeastern Asia that were once placed in Barilius. The atlas files it with the Indian and Sri Lankan barbs for the shared genus. No widely used English common name is recorded.
Morphology
A slender stream danionid. FishBase gives a maximum of 4.5 in SL for males and unsexed fish. Colour pattern is not described in the sources the atlas uses.
Habitat
It occurs in the Chao Phraya and Mekong basins. FishBase describes adults as living over gravel in clear, swift, small streams and in rapidly flowing stretches of large rivers.
Feeding
FishBase reports that it feeds on insect larvae, especially those of dragonflies and damselflies (Odonata).
Mating
Mating behaviour is not described.
Breeding
Reproduction is not described, and no captive spawning has been documented.
In the aquarium
FishBase gives no temperature or pH range for this species. The habitat it records, clear, fast, gravel-bottomed water, indicates a tank with strong current, high oxygen and a tight lid, with live or frozen invertebrate foods. Keep it in a group. FishBase notes that it is rarely seen in markets.
Conservation
The IUCN Red List category is Least Concern, assessed on 17 February 2011. Specific threats are not described.