Hi, Welcome to AquariumAdvice.com!!
Any type of unwanted algea growth is ussually the product of having too much nutrients in the water. High nitrates and PO4
can be causes. The first thng you should do it test both your tank water and source water for nitrates and phosphates. If you are using tap water as a source that could be a problem. Evaluate your feeding schedule, chances are you can cut back by a lot in that area. What type of lighting do you have, how long do you run them and how old are the bulbs?