Tsengwen

The genus Acrossocheilus is restricted to southern China, northern Vietnam and northern Laos. It can be distinguished from related genera by the following combination of characters: rostral fold present; lips fleshy and continuous around corners of mouth; lower lip with a median interruption; mouth inferior; horny sheath on lower jaw; two pairs of barbels; last simple ray of dorsal fin osseous with a serrated or smooth posterior margin.

Current knowledge suggests that H. formosanus is the most widely-distributed and following Chen and Fang (2009) it can be distinguished by the following suite of characters: 3+7 dorsal-fin rays; 10-12 pectoral-fin rays (modally 11) +9-11 (modally 10)...

This species may not yet have appeared in the ornamental trade but it has been collected by a few individuals. It can be told apart from related species from Taiwan by possessing 30-32 longitudinal (lateral) scales vs. 32-39 in other species, and 6-8 scale rows between the origin of the first dorsal-fin and upper pectoral-fin base vs. 9-15 in other species.

This fish is normally imported alongside the congener R. candidianus and is actually the commoner of the two in the aquarium trade. It looks very similar to R. candidianus but does not grow as large and possesses a more rounded snout. Most specimens also have spot-like markings on the sides of the head which has led to them being identified as R. nantaiensis, but the fish do no...

This species is a relatively recent addition to the hobby but considering the number of specimens allowed to be collected for scientific research is highly restricted by the Taiwanese Council for Agriculture it seems odd that it's become available at all. Indeed it appears that those in the trade are collected and exported on an illegal basis (T-Y Liao, pers. comm.)...