Just bought some Hornwort at the local mega-LFS (TFP in Lancaster) and did a Potassium Permanganate dip to try to kill the snails that came along with it (I don't mind the tiny ramshorns, but I don't ever want to have MTS again!).
After removing the hornwort for rinsing (it's not in my tanks yet), I saved some of the water at the bottom of the bottle to observe the snails for a few hours and make sure they're actually dead before I move the hornwort into my tanks. After letting it sit for a while, I came back to see if any of them had moved (not yet) and discovered a critter I'd never seen before swimming around! I looked through this thread, but I haven't seen anything quite like it.
At first glance, you'd never be able to tell them from the other hornwort needles that fell off in the container: they're no more than 1/4" long, very slightly thicker than a hornwort needle, brownish-green, and their bodies stay perfectly straight when they swim (propelled by tiny, invisible legs). I tried to take a picture, but they're so small there's no visible detail. They are the two top-most "needles" in this picture below. Any ideas what they could be?
Oh, and BTW, finally made it to 100 posts!!