Can you send a picture? Depending on how much of it is spreading will determine the lengths in which you may need to go to fix it. First: try dosing with flourish excel; read the directions on how much to use. This does not necessarily kill it, but it should stop it from spreading. Also investing in some real Siamese algae eaters won't hurt. If it still persists, because it's a nasty one, you may have to take out the plants, decor, and equipment that this hairy bugger is on, and wipe down with good old hydrogen peroxide and water mix. Yes, the kind you would get at the local drug store. And of course conduct PWC's early and often.
Let us know how it goes.