you should be lucky that you just have hair algae, I got a bryopsis problem that is slowly causeing me to die. Yes thats right it is turning my hair gray and i think it might even at time cause my blood preassure to rise so high I have a heart attack. dip those rocks in peroxid 50/50 water salution use a clean cleaning brush and go to town then rinse in clean salt water. start on one side of the tank and try not to do all the rocks at once, because you tank could recycle. But you have to remember that you have to find the true cause of the phosphate causeing the growth weather its over feeding inproper lighting or live sand or rock loaded with phosphates. try running some gfo