reef algae

I have this greens algae, plucks off easy, doesn’t like direct peroxide. Purple urchin slowly eats it. I have GFO running 0.17 nitrate 0.002 nitrites 0.01 phosphates calcium 400 magnesium 1380 alkalinity 8.2 pH 8.1 and salinity 33 ppt I want to get rid of it as it’s outcompeting my coral frags...