Join Date: Nov 2007
Location: NYC & Long Island, NY
I have a colony myself, which I keep not because they're useful, but because I find them interesting. I have not found them too useful in algae cleanup (as they're relatively small snails and sooo slow), but they did seem useful when establishing the tank, and they helped clean up a lot of the leaves that died back as my plants got established. They only seem to burrow an inch into the gravel at most, so I'm not so sure they'd eliminate dead pockets in deep sand.
As far as the snails contributing waste... most people don't feed their MTS so any waste they produce is waste that was in the tank anyway, I would assume. They just convert it to another form.
My opinion: Get them if you like them, not because you want a cleanup crew.
I should add tho, if you search for MTS on youtube, there's a great video of them eating algae off glass. I wish mine did that. Heh.