After googling images, it does look like subwassertang. Guess that's why I couldn't find it on any algae-identifying pages.
What is this stuff? I've never heard of it, nor did I introduce it purposely.
It first appeared about a year ago on a peice of driftwood in the tank that i've since removed. However, it looks as if it jumped over to another peice of driftwood.
It is slow growing though. I guess i need to do some research now.