Holy @#$@(#U#@!!!!! It's a Hydra INVASION!!! I took a tiny piece of an aquatic plant (plus a couple of chunks of algae) from a stream, and it had HUNDREDS of Hydra on it! I've never seen so many Hydra in my life, I usually have to take a ton more material to get one tenth of the number of Hydra. What sucks is that I don't have anywhere to keep them in the long run, and I don't even have anything to feed them in the short run.
I'm also surprised they were found in a stream, I thought Hydra were mostly lentic organisms.