I have posted a couple of times about using nerite snails in cichlid tanks (search the site for those posts). If you aren’t familiar with them, let me add something that I didn’t mention previously. Though you may upright some snails that you find upside down, don’t expect them to always start moving immediately. In fact, sometimes you’ll see an upside down snail and the aperture will look empty. Neither means the snail is dead.