Water flea
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 Diapthomas. Water fleas are commonly sold as aquarium food since they are easy to culture and reproduce rapidly.