Pure Reef is excellent. Probably one of the nicest LFS I have ever been to.
They have had some interesting fish (Gem Tang, Bat Fish, several types of butterfly's/angles/tangs) along with most of the usual ones. Lots of coral and other inverts too.
That part of Alpharetta is pretty busy during the week especially after 3. I usually go early.
If you call they always answer and are very nice.