It just appeared and it has been growing pretty fast. I purchased a sand sifting star and urchin a few months back so i think they might have brought it in the tank, but have no idea what it is!
No, it was attached to some live rock for some time and then the other day it was on the back of the urchin. He let it go after a water change was done this morning.
Yeah i would say its definitely a semi-bleached red algae. Nemastoma sounds like a good guess but it seems to lack the swollen sacs at the branches of each "leaf"