I don't know if you can tell by a picture or not. I never see any polyp extension, unless its happening at nite when the lights are off. The first pic is when I first got the coral from the LFS about 2 1/2 months ago, the second pic is from last nite. The color on the coral is a, jmo, deep purplish color, when the MH lights are on its looks a brownish color.
