| | Re: Mts?
IME they don't tend to make messes, but they are good for keeping things from getting anaerobic. They call them snails for a reason - their rate of movement isn't terribly disruptive.
I do agree that they multiply like whoa, though. I don't mind it so much since they make good food for my loaches, but they are rather pesky if you have nothing to control the population.