I have the same snails in my tank. I have one larger one for sure...almost a half inch long. I havenít started squishing them yet (at least not as much as I squish the pond snails) because I kind of like the way their shells look. I never really thought about them being harmful to my plants. I haven't noticed any plants with holes in them, and come to think of it, I have never seen these guys on any of my plants or the glass...I only see them on the substrate or half buried just below it. Sometimes the only way I know they are in my tank at all is because once in a while Iíll see a speck of gravel move from them under it.