Try a peroxide dip. Mix about 2 cups of saltwater with 3/4 cup or so of regular peroxide. Dip and soak for a few minutes. Rinse in saltwater and then put back in the tank. The algae will start turning brown and eventually die off in a few days.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.