If you ask a gardener, "what do snails eat," you will get a very emotional answer. Snails are notorious for eating green leafy plants such as cabbage and lettuce as well as fruit. Snails also eat the leaves of some other crops while destroying the health of the edible parts of the plants.
Whether you grow fruit trees or broccoli, you need to watch out for snails. Broccoli, eggplant and most root vegetables start out as green leafy plants. Garden plants are most vulnerable in their early stages. When a snail eats even a small portion of a baby plant, the plant may die before it matures. Snails can also climb trees and eat your apples, peaches, cherries and other fruit crops.
Other than garden vegetables, snails often eat plant matter that is decaying as well as algae. Some types of snails are carnivorous and eat crustaceans such as mussels. A carnivorous snail will "drill" all the way through a mussel's shell to eat the mussel.
One lesser known item in the snail diet is calcium. Snails eat calcium directly from rocks. Calcium is necessary for a snail's shell. Limestone is a prime example of a rock that is high in calcium. Snails scrape the calcium from the rocks with their tongues.
If you have practical reasons for wondering what snails eat, maybe it's better to ask yourself what eats snails. If you have a crew of children handy, you can give them a fun ecology lesson by instructing them to hunt for snails and introduce the snails to the chickens.