Loaches are freshwater fishes of the family Cobitidae, small benthic (bottom-dwelling) fishes with a flattened ventral profile. There are 160 different species of them. Loaches are mostly scavengers and are omnivorous, usually not very picky about their food. They may eat aquatic crustaceans, insects and other small invertebrates as well as scraps of organic detritus. Many live in waters of generally poor quality and feed on tubifex worms which are associated with those areas. Some have adapted to less-than-ideal water conditions by being able to gulp up atmospheric oxygen from the air. Loach species are distributed through Eurasia and in Morocco. They mainly inhabit rapid-moving streams.
Because of their scavenging nature and their ability to adapt to many freshwater ecosystems, some loaches have been introduced to waters in regions which they are not native to and may pose problems to local wildlife as an invasive species.
The body forms of various loaches range from being vermiform (worm-shaped; long and thin) to Fusiform (spindle-shaped; cylindrical and tapering toward the ends). Most loaches do not have true scales. Like catfishes, loaches have the sensory organs known as barbels; usually 3-6 pairs of them. Some other characteristics of loaches are a small bottom-facing mouth suited to their scavenging benthic lifestyle, an erectile spine below the eye, and a single row of pharyngeal (throat) teeth.
Some loach species are popular as food fish in East Asian countries such as Japan. They are of importance in the fisheries or being raised in aquaculture. Some species of loach may occasionally be caught for bait.
Many of the more brightly-colored loach species are popular with freshwater aquarists and are therefore of importance in the aquarium trade. The more colorful tropical loaches that are kept as pets mainly come from South Asia and South-East Asia.
Loaches often encountered in aquarium trade
Horseface Loach ? Acantopsis choirorhynchus
Longnose Loach ? Acantopsis octoactinotos
Weather or Dojo loach ? Misgurnus anguillicaudatus (although Misgurnus fossilis and Cobitis taenia are also referred to as weather loaches).
Kuhli Loach ? Pangio kuhlii
Clown Loach ? Chromobotia macracanthus