Nusiance algae needs 3 things to live: water, light and food (excessive nutrients). You can't eliminate the water, the corals need the light, so you must remove the excess nutrients.
What is your nitrate level?
Have you tested for phosphate?
Do you run carbon and if so what brand and how often do you change it?
How often do you do water changes and what kind of water (tap, well, RO
, etc) do you use?