I would try not having the halides on as long at first (do you have any additional pc lighting?), add some nassarius snails, and possibly cut down on how much you feed. Some goby's are also good sand cleaners...I have a dragon goby. Only issue is they dump sand on your corals at times. Those would be my first steps to help with brown algae growth. Of course I didn't ask the normal questions like how long have you had your system up and running, water params, etc.