We have a large mud bottom pond (110' x 50') that is coming back to life after the previous owners put herbicide into it. Last summer there was a healthy clump of red ludwigia that spread slowly, and some kind of grass that has extremely sharp stems or leaves.

This spring I noticed a big clump of something new. I thought it was algae at first but i don't think so. It's not small pondweed--that has leaves like narrow blades of grass and this has just hair-like leaves. Or whatever they are. It is rooted in the bottom, I guess (hard to see) and frogs and fish seem to like it to hide in.

This little branchlet is about 5" to 6" long total. I've looked all over the internet and couldn't find anything that looked just like it but there are a lot of photos of stuff that don't show a single plant or branch, so it's hard to tell.