Sorry about all the recent posts here, but I'm anxious to learn.
What are the benefits of adding snails to your aquarium? Disadvantages?
I've heard they burrow in the substrate too, do they prefer sand over gravel?
The answer to your questions depends on the species of snail, some are pests and eat your plants, some are good and just eat algae/left over food. Have a look in the inverts/amphibians section and also at http/www.applesnail.net