Freshwater snails are omnivores, and they typically subsist off of the algae and food debris in a fish aquarium. Include aquatic plants for your snails to graze on as well.  Check with your vet or a clerk at your local pet store to find out which types of fish live best alongside your species of freshwater snails. If you don't have fish in the same aquarium as your snails, you can purchase small algae discs. Follow the instructions on the packaging, and provide the right number of disks for the number of snails in your tank.  Algae discs are readily available online or at most pet stores. In addition to algae, freshwater snails enjoy a diet of blanched vegetables. Blanching involves dipping veggies into boiling water for 2 minutes before dunking them in ice water. Freshwater snails especially like to eat shelled peas, carrots, cucumber, zucchini and iceberg lettuce. Allow the blanched vegetables to cool completely, then add them to your aquarium.  Chop or shred add vegetables into pieces smaller than a time. Begin by adding a small amount of blanched veggies each morning, and gauge how quickly your snails can finish them. Add a bit more or less until you notice that all of the food is being eaten in 12 hours or less. Remove uneaten produce after 24 hours. Just like land snails, freshwater snails require calcium to keep their shells healthy and strong. Provide a calcium source that your snails can nibble on, as a supplement to your snails' diet. Some sources of calcium for freshwater snails include:  Cuttlebone Shells from dead snails Oyster shells Natural limestone (be aware that this may raise your pH levels) How much, how often, and what you feed your snails will vary based on their species, the number of snails in your tank, and what other aquatic life shares the aquarium with your snails. The best course of action is to speak to someone at the place where you purchased the snails, or consult a vet.  You may still need to do a bit of trial and error to figure out exactly what your snails like. If your...

TL;DR in Chinese:
将淡水蜗牛和鱼养在一起。 在鱼缸里投放绿藻粮。 给蜗牛喂食焯过水，并且切得很细的蔬菜。 为淡水蜗牛补充额外的钙源。 向宠物店店员、专家或者兽医咨询蜗牛的饮食习惯。