Reefermike,
I'd scrap the algae off ASAP! I waited to long and it grew thicker, luckly I have a 66 gallon tank which is glass and used a metal razor (I know not to use a metal razor but the plastic razor wasn't sharp enough). Plus help with two yellow tangs which did a hell of a job eating about 50% of them or atleast trimming it down to the thicker portions. Since you have a 12 maybe a small tang could help as a more natural problem solver.... then you can sell him back to your LFS after everythings cleared out..... Good luck..