So an anonymous GR reader has solved the crazy furry-green-thing mystery, which I wrote about months ago. They are Cladophora aegagropila! You can also call them Japanese moss balls (as they are considered a national treasure in Japan) or Russian Moosballen, like the Germans do. Aqualand explains all. Scroll down to the science experiment in which they dismember a bunch of the Cladophora to see if they'd regenerate, kinda like Gremlins. Afterwards, check out the rest of their site, it's pretty rad. And then maybe purchase some Axolotls:

But watch out, they're "frequent biters of tank mates."

On second thought, just get some bunnies.
As Aqualand says, "Everybody loves bunnies."