I have a 55 gal. African Cichlid tank that's over run with MTS. Yeah, I know that it's because I've fed too much, and yes., they are (relatively) harmless. The problem I have is I am (temporarily) forced to overcrowd my Africans, and so I use two large HOT filters to dispose of excess nitrates, etc. The darn snails are clogging up the filters, stopping the water flow, etc. I'd like to say, net the suckers out, but the stone grottoes needed for the safety of the crowded fish make this a losing proposition. copper sulfate (Had A Snail brand) doesn't seem to do the job, even without any charcoal, and in spite of hard alkaline water. I can't seem to kill any noticeable number. With the number of snails I see when I "visit" the tank at "Oh-Dark-Thirty", I would think I would see some carcasses (shells?) after treating the tank twice. My substrate in the tank is coral sand.