ALveopora

I bought an alveopora about 2 months or so ago and it had been doing good ( i think anyways) but recently it seems to keep it polyps in and doesn't fully extend them. My water quality is good, except for all of my hair algae, some of which is growing on the alveopora. I tried to pull some of the algae off, but it just comes right back. What, if anything could I do? Here are some before and after shots, the second pic you can vaguely see some of the hair algae in the center of the coral.

Thanks Mogurnda, I finally find some info on them, and that's pretty much what it said. I've been fighting this hair algae, and reducing nutrients in the water, so that's probably why it's starving.