I have this brown algae that keeps on growing on my main rock and gsp. Every week I have to brush it with a tooth brush but it always comes back. I always have high phosphate at 0.25 but my nitrate is always at 0. I was just wondering if I should dose nitrate to help balance out the elements to stop this algae. The tank is 2 years old. I do 20% water change every week and clean the substrate every week.