Ckoladawn, I agree, the Aquarium is a great store. They are pricey but high on quality and selection. There is also a good saltwater only on Bearden Hill.
Jermpool, in Chatt I have been to Bermuda which I thought had pretty good quality and an ok selection. I also visited Fish Mania.
I forget the name right now, but Chattanooga has arguably one of the best pond stores in the southeast. I had known its reputation for a while, so it was one of the first places I visited when I came to town. Unfortunately, a pond store does little good for someone living in an apt. ;)