What do you think of this algea? (pics)

[mademperor]

My old rocks had this algea grow on it. I've since removed all the rocks besides this one. I will be replacing this rock on thanksgiving.
Any idea what it is, how to prevent it?

Oh yeah, that algea grew before I got the plants and before I started dosing Excel.

http://ronpaulny.com/media/algea.jpg

[GirlieGirl8521]

Is it slimy feeling or more fuzzy-like? It looks almost like cyanobacteria to me, which can be caused when nitrates bottom out in a planted tank. The fact that you got it before the plants tells me its probably something else though.

[damon]

I prefer a little algea on rocks and driffwoods, it makes it looks more natural. Just dont let it get out of control. It's a nice looking rock by the way.

[flyfly]

definitely cyanobacteria, also known as blue-green algae.