I have them coming out at night as well. Seems as though they disappear during daylight and they retreat to the sandbed or any other crevice that they can hide in. They must be breeding in the water column.
The only effective way was either to kalk it (may get on something else) or take the rock out and peel that greyish base that it has off the rock (the only sure way).
That is great so when I walk right in I can see all the goodies right in front of me! You should think about putting a TV in the wall above this new frag tank so that you can look at the tank and watch the Caps game at the same time.
I thought I got some at Lowe's before, I think they came in a plastic bag and were not necessarily in the sorted bins where they sell them individually like the stainless steel fasteners.
I have mine on the bottom too. Mine got covered with a little sand and turned that portion white. I get good polyp extension when conditions are proper in my tank, so you are on the right track!
Sorry if this has been discussed before but I just checked out this guy's blog about collection and aquaculture of corals and thought it was pretty interesting.
http://eddie-coral-adventures.blogspot.com/
I have two of them and they really do pop the colors but it seems I may need at least six of them to get the coverage over the whole tank since their beams are so narrow.