Unwanted algae growth is a function of three things...Water, Light and Nutrients! Use RO/DI water, use the proper lighting spectrum for the appropriate amount of hours in a day for a light cycle and quit adding nutrients to the tank and it will go away if you have much in the way of a clean up crew!
Most algae problems in this hobby are a result of over feeding your fish and corals or too many fish in the tank. Most of the time when you have an algae problem you also have a water chemistry problem to go with it as a complication to the root problem. I dont care what reading you get on a Phosphate test, if you got algae its too high!!! That algae is just soaking up a lot of that phosphate so your test aint detecting it accurately.