This is a snail in our fish tank. The Planorbidae are by far the largest family of aquatic pulmonates that are widely distributed over the world. Three subfamilies are recognized in the Planorbidae: Rhodacmeinae, Buliniae and Planorbinae, the latter two are subdivided in tribes, each consisting of several genera. However, there is much discussion about many of the genera and the species. Many genera and species are considered to be invalid and synonyms of each other by several authors.

The subfamily Rhodacmeina contains one genus with three species that all live in the Tombigbee (Alabama) and Tennessee river drainage in the southeastern U.S.A. The widely distributed subfamily Buliniae consists of three tribes: Bulinini with four genera: Bulinus (Africa, Madagascar, western Asia and southern Europe), Indoplanorbis (southern Asia), Laevapex (eastern North America) and Gundlachia (South and Middle America).
Physastrini with possibly 12 valid genera: Glyptophysa (south-eastern Australia, Tasmania, New Zealand and New Caledonia), Physastra (Australia, New Zealand, New Caledonia, Sumatra, Philippines and several Pacific islands), Ameriana (north and north-east Australia, New Guinea, Indonesia, Thailand and the Philippines), Barnupia (tropical Africa), Ferresia (North America), Pettancyclus (Australia, New Zealand, East and southern Asia and eastern Africa), Isidorella (western and southern Australia), Bayardella (Australia), Patelloplanorbis (New Guinea), Oppletora (north Australia), Ancylastrum (Tasmania) and Miratesta (Indonesia). Camproceratini with two genera: Helisoma in North America and Planorbarius (North America, Europe and northern Asia).