Moina is a genus of crustaceans within the family Moinidae. The genus was first described by W. Baird in 1850. They are referred to as water fleas but are smaller than their more well-known cousins: the larger Daphnia magna and the medium-sized Daphnia pulex. This genus demonstrates the ability to survive in waters containing low oxygen levels as well as high salinity and other impurities, including salt pans, and commonly eutrophication. An example of such an extreme habitat is the highly saline Makgadikgadi Pans of Botswana, which supports the species Moina belli prolifically.