It's called green carpet moss. I had some for sale but it's all sold out if you want some in the future let me know.
Over time does it go away
oooooooo that moss is really interesting, I actually think ive got some of that from the wild by accident!
Do you have a closer pic of the fronds? I might just happen to have JUGS of that stuff growing in my bathroom in containers, sense i collect moss in general! And yeah the fungus goes away eventually.. heh snails will take care of it and some fish even nibble on it. totally harmless (just not to the eye :P )