Water flea is a generic term for a number of small aquatic crustacea characterised by their jumping or jerky mode of swimming. Most are between 0.1 mm and 3 mm in length. Most commonly, they will be species of Daphnia but a number of other genera are also commonly included, including Cyclops, and Diaptomus. Water fleas are commonly sold as aquarium food since they are easy to culture and reproduce rapidly.

The populations of several water flea species are considered threatened. The following are listed as vulnerable by IUCN: Daphnia nivalis, Daphnia coronata, Daphnia occidentalis, and Daphnia jollyi.

Crustaceans

Watervlooien