Water snails are herbivores whose diets consist of algae and other forms of vegetation. Both in captivity and the in the wild, water snails adapt their diets to eat nearly any type of vegetation or micro-organism that is available in their habitats.

Partially as a result of their adaptable tastes, water snails are notorious overeaters and overbreeders. When two or more snails are left in a tank with an abundant food supply, they are known to quickly reproduce and eat all of the vegetation, including plants that were put in the tank for aesthetic purposes. In the wild, water snails become a destructive invasive species when in a habitat where there are no natural predators to keep the population under control.