The minute moss beetles (Hydraenidae) are small species with various body shapes, living in different types of waters. Formerly they had been classified with the water scavenger beetles (Hydrophilidae). Despite their aquatic lifestyle they are not able to swim. Worldwide about 1500 species have been described, in Germany 52 species are known to occur. They are highly specific in their habitat requirements: The species of the genus Hydraena and Ochthebius are usually found in flowing waters (also in coastal regions), whereas the genus Limnebius prefers stagnant water or quiet streams (e.g. walls of wells covered with moss). The species are phytophagous, both larvae and adult beetles of the terrestrial species feed on plant detritus, whereas the aquatic species feed on unicellular algae.