I've had these small snails in my tank for years. They're awesome in that they survive. I keep cleaning the glass, and whether or not some die, lots and lots live.
Look at it this way -- if you stop cleaning the glass (to insure that you kill nothing -- because if you have these, you most likely also have pods on your glass...), you won't ever see the beautiful tank you have worked so hard to create!
I usually clean my glass with an old plastic card and not with a scrubby-pad. That way, the pods and tiny snails just fall to the bottom and then crawl right back onto the glass once I've cleaned.