There was a reefer here named Jung a while back and he traveled a lot for his job and almost did no water changes. Relied heavily on over skimming. Any rate he had those types of algae infested all over the rocks and at that point, you can't get rid of them.
As Breakin Newz said, get rid of it now.
Suck it out, you do not want to get any little pieces of that algae into the system. Otherwise, like said before it will spread like wild fire. I recommend a turkey baster.