Apple snails are often kept in fresh water aquariums. They do tend to chew up plants pretty bad, so they are not suitable for fish tanks with delicate plants. Apple snails also eat fish food scraps.
Apple snails.
Apple snails are edible by humans, although it is probably a matter of taste.
In lots of places apple snails are considered to be pests as they do eat a lot of plants, so if you buy apple snails for your fish tank and get bored of them do not release them into the wild.
Apple snail.
Further readings:
applesnail.net
A recipe for cooking the golden apple snail
Last updated: July 3, 2014