Water snails are a cleaning weapon in biological pools, and so welcome. Almost all species feed on the so-called biofilm, a living film of microbes, algae and fungi growing above any surface as long as there is enough water. Snails have a strong muscle, a kind of “treadmill”, which serves to move them above these surfaces. Some species are even able to walk like this hanging underneath the water surface, as long as it is completely calm. They take advantage of the capillary forces of water molecules and clean this liquid “surface” as well.

In biological pools, a very common and easy-to-recognize species is the great ramshorn (Planorbis), for its flat, brown-colored shell and very snaily. This species likes clear waters and is therefore rare to find in nature. The snail likes to climb on plants where it is also scraping the biofilm that settles above them. Whoever removes the snail from the water and puts it in a glass to observe it, can see the “beak” in constant action through the glass. Don’t forget to return the snail to the water!