Parasites eating freshwater plants?

I noticed one side of my aquarium having a large number of small 3 mm
sized white worm looking creatures on it (maybe 1-2 mm in size, pretty
small in other words), should I be concerned about them eating my
plants? You may have noticed my previous post about my plants and
already know my plants stopped growing. Some small (I think they are
called mystery snails because I can't find reference to them in my
books) 2-3 mm in size red snails came with the elodea I bought 2
months ago and have multiplied and are in my aquarium - should I be
concerned about them eating my plants or are they harmless? I am
pretty sure that they are harmless from what I can tell. Thanks all -
later.