A freshwater fish of the loach family. Length 16-25 cm, rarely larger, weight 25-40 g, sometimes up to 50 g or more. The body is elongated and covered with fine scales. The head is small and elongated forward. The mouth is directed downwards and surrounded by ten antennae, the shortest four on the upper jaw, two in the corners of the mouth and four on the lower jaw. The eyes are small, located on the forehead and yellow. 

Fins are small and the tail is rounded. Colouration depends on habitat. The back is brown with numerous small dark spots, the belly is yellowish and also spotted. A broad dark band runs down the centre of the body, with narrow, short bands above and below. The fins are brown, with dark spots on the dorsal and caudal fins. It lives in the rivers and lakes of Central and Eastern Europe. In Russia it lives in the basins of the Baltic Sea, the Volga, the Kuban and the Don. It is often found in overgrown and silty lakes, ponds and canals with stagnant water. It is able to burrow into the silt and survive in unfavourable seasons. In oxygen-deficient conditions, it can breathe using an additional respiratory organ, a small section of the hind gut that is woven with a large number of blood vessels. Sexual maturity occurs in the third year of life. Spawning occurs from April to June. Fecundity 100-150 thousand eggs. Feeds on bottom invertebrates. No commercial value.

The loach is very undemanding and can live in places where there are no other fish. It can breathe through its gills, skin and intestines. When oxygen is scarce, it rises to the surface, sucks in air with its mouth and passes it through its intestines, making a squeaking sound. When a body of water dries up, the loach hibernates, reducing its need for oxygen. When a body of water dries up, it burrows into the mud and does not return to the water until after the rains. As a result, the loach can be found in heavily polluted lakes, rivers and ponds where it rests permanently near the bottom or sinks into the mud. In such places they are found in schools. The loach is largely inactive during the day and only goes out to feed at dusk and night. It feeds on invertebrates, insect larvae, small crustaceans and bottom dwelling molluscs.

They spawn from April to June. Females are very fertile. For example, individuals from the upper Dniester, 17-24 cm long and weighing 44-140 g, had 11.6-38.7 thousand eggs. The larvae appear after 7-8 days at a water temperature of about 15° C and are no more than 5 mm long. The loach grows quite intensively. In the upper Dniester, for example, the annual growth rate during the first three years of life is more than 4 cm; at the age of three, the fish reach an average length of more than 13 cm. With the onset of sexual maturity, the growth rate decreases and the body length of five-year-old loaches is 18-23 cm. Sexual maturity occurs at three years of age.