Hi Jake,
As far as quality Aquarium-only stores; there are two (2) in the NWA area; Worlds Underwater and SeaFari. Worlds Underwater is located in Johnson, AR (it's a tiny town that is practically inside of Fayetteville) and SeaFari is located in Rogers, AR. Of course we have the usual PetSmart and PetCo, but....do I really need to say anything about those guys?
I'll have to second the above comment by Staggs; Worlds Underwater is a great store for both freshwater and saltwater/reef hobbyists. Their staff are all very knowledgeable on most all topics of the business and best of all is their variety of selection:
They are always getting in new livestock of FW and SW fish and they have multiple big coral and frag tanks with a huge variety. Their FW aquatic plant tank is very nice and is always changing as they get in new plants. (Never had a snail from these guys either) They also sell a lot of equipment, rocks (dry rock and wet live rock). They have a big selection of of used ready-to-go tanks that customers have traded in for new or other equipment. They sell RO/DI water and Saltwater by the gallon.
SeaFari is a smaller store in Rogers. I have only been there a handful of times and the times that I did go they were very helpful. They don't have quite as big of a store or the selection that WU has. They do have a rather large aquatic plants section which, for me, is nice, because I am currently building several planted aquariums and it's nice to have a variety of plants to choose from that other places might not have.
That's my two cents...
Josh