MTS stands for malaysian trumpet snails. I have these in every planted aquarium i set up, they are IMO brilliant!
They generally stay in you substrate during the day but after lights out the emerge and quite literally eat any algae they can find. They can reproduce very fast but iv never really had a problem with them as i keep my aquariums quite clean (weekly water changes, remove uneaten ect)
From my experience they are great at removing algae from plants without harming them. In fact the only time they will snack on plants is to eat any dead or dying parts of the plants which actually helps the plants out. They also do a great job of keeping your substrate airated and clean,as they are constantly burrowing around. They also do a great job on the aquarium glass.