Its cyano or BGA Blue Green algea, same monster different color. Treatment is best when the cause is identified. What size tank how many fish, how often do you feed and how much. Do you feed corals and how much, and how often. What type of lighting do you have? is it new? Have you changed your bubs reciently? How much flow is in your tank?
All things that could answer why you have it. To help get rid of it you can reduce the time your lights are on to a few hours a day for a week or so. Syphon as much of it out as you can, and increase flow in the affected areas.