Lil Ginger, Probably not, since they can live in some of the most polluted pools and ponds in nature. I would at least change the water often, though. I read that ramshorns and can breath oxygen, which allows them to live in water with very little of it. All that said, in a little 3 gallon jar like this they probably don't need a filter, I just added a little sponge filter because I had one that I wasn't using and an old air pump handy.
Anyone know if Cherry shrimp will eat baby snails, or snail eggs?