Sponge or algae?

[ThrowedToad]

This stuff has been on my rock since about a week from when I got it. At first I thought it was algae but now I am thinking different. It looks like it is taking some type of form, kinda like a q-tip sponge. Looks kinda crappy and is not removed with boiling water or scrubbing with a toothbrush. Any Ideas?
http://i119.photobucket.com/albums/o154/throwedtoad/S7303497.jpg
http://i119.photobucket.com/albums/o154/throwedtoad/S7303515.jpg
Thanks all.

 

[Fluff]

It's a sponge.

 

[melosu58]

Agreed. Sponge. Excellent filter feeder