Algae will bloom in new tanks, especially on dry rock. Phosphates may make it a bit worse, but you're going to have an ugly stage until the tank starts to find a balance and begins to establish populations of non-pest algaes. When the rock starts turning colors other than white, that means it's growing a population of slower-growing algaes (which need nutrients to grow) that will gradually help to outcompete the opportunistic pests.
When you see a decent bit of algae, add a good cleanup crew. Check out ReefCleaners.com for some ideas. You want lots of snails, maybe a couple hermit crabs if you like those. Pull out long tufts of hair algae by hand (snails can only eat short stuff), keep your nutrients reasonable (NOT zero), and ride it out.