Gastromyzon is a genus of fishes found exclusively on the island of Borneo. Species in this genus, known as torrent loaches, are obligate bottom-dwellers and exhibit extreme morphological adaptations for life in torrential waters. They have a streamlined shape, wide head, and tapering body. They are poor swimmers and have lost the ability to hover or swim in mid-water. As a consequence, fishes in this genus have evolved new modes of locomotion, which involve creeping and crawling along the bottom and around submerged rocks. In most species, the ventral side of the fish is flat, made up of fused disks. Torrent loaches orient themselves facing upstream, clinging to rocks to avoid being swept downstream with the moving water. They tend to show coloration patterns that allow them to blend in with their environment.
Torrent loaches generally inhabit small, clear, fast moving waters with a rocky substrate. They range in size from 5 to 10 cm. Their diet consists mainly of algae, which they scrape off the rocks to which they cling.
(Inger and Kong 1961; Tan and Leh 2006; Tan and Sulaiman 2006)