Barbatula, the stone loaches, is a genus of small bottom-dwelling fish in the family Nemacheilidae, with an unusually broad range across the Palearctic — the atlas's 27 species are drawn from as far apart as China, Mongolia, Russia, and North Korea in the east and France, Austria, Albania, and North Macedonia in the west. They are elongated, largely scaleless fish with a row of barbels around a downturned mouth, adaptations for feeling out invertebrate prey among gravel and stones in cool, well-oxygenated streams and rivers. The type species, the Stone Loach (B. barbatula), is the most familiar and gives the genus, and much of the group, its common name.
Stone loaches are modest, unassuming aquarium fish rather than showpieces — hardy bottom feeders best suited to a cool, current-fed tank with a fine or gravel substrate they can sift through, alongside other calm cold-to-temperate-water species. Few Barbatula beyond the Stone Loach and perhaps the Spanish Stone Loach (B. hispanica) or Siberian Stone Loach (B. toni) are ever offered in the trade; most of the genus is known chiefly from regional ichthyological surveys. Conservation data lag badly behind the genus's real diversity: the great majority of species in the atlas are Not Evaluated, and among the few that have been assessed, two are listed as Endangered — a reminder that many of these narrow-range stream specialists have never been formally reviewed.