Have you added potted plants recently? If so then that is probably what it is. Manually remove it as much as possible and it should be ok. If you see it begin to grow or spread then maybe a more indepth investigation can begin
It's probably not Hydra, from your description, but fyi on Hydra.
Here's some info:
Hydra is a genus of simple fresh-water animals possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted freshwater ponds, lakes and streams in the temperate and tropical regions by gently sweeping a collecting net through weedy areas. They are usually a few millimeters long and are best studied with a microscope.
Hydras mainly feed on small aquatic invertebrates such as Daphnia and Cyclops.
All species of Hydra exist in a mutual relationship with various types of unicellular algae. The Hydra affords the algae protection from predators and in return, photosynthetic products from the algae are beneficial as a food source to the Hydra .
Info from Wikepedia
Sara, I think I've read that they can be predatory towards tiny newly hatched inverts, i.e., shrimp, baby snails, but otherwise pretty harmless. Correct me if I'm wrong Petluvr.
See, in this pic you can see the green stuff that I didnt manage to remove that is wrapped around the plants that come with the little buckets holding their roots... some of it is exposed and I am thinking that during the waterchange it got knocked loose and separated and is floating around... I am hoping this is what it is... it makes the most sense???
I mean... most of it is resting on the java moss... it actually kind of looks like the fuzzyness of brine shrimp but I have never fed this tank brine shrimp so its not that.