Aiptasia

[whaase]

I have noticed this thing on the bottom of a rock I have. It only opens up fully when the lights are off. It has moved around a bit. It looks like some pictures of aiptasia I've seen, 1/2 across, brown. When I pulled the rock out of the water to get a closer look, it closed up like a polyp. This is the only one i can see in the tank. I tried to get a picture, but I just can't get a close up shot in my tank for some reason... Any ideas?

Walter