Thats the best I can explain it. Miniscule transparent sacks of something attached to the glass. I just noticed them today. What are they? I wont be able to post a pic, they are way to small.
What fish do you have in your tank and what size is the tank?
Control feeding. Overfeeding is often the main cause of overpopulation and you want to avoid that. Pick out every snail you can see or bait them using a lettuce weighed down by an object. Dispose the lettuce containing several snails clinging to it.