This stuff started growing on a piece of liverock i got. I think it is considered nuisance algae (Scroll algae, Padina i think), but my tank was FO when it started, so i didn't mind. I only bad thing i can find about it online is that it can take over a tank (someone correct me if this is bad stuff). I think it looks cool in FO tanks or others . It was growing great in my tank with normal output florescent.
Here's a picture when it first started growing. 3Jan09
Here's some pictures today. It has not spread from the rock, it has just grown more dense 28Feb09
Let me know if you want some.