I have only been to a few in Orlando but this one had a nice selection of livestock: Fishy Business Aquarium
140 S Hwy 427, Longwood, FL
Phone: (407) 331-4882
Prices were a little high but the livestock looked good.
Also if you want to consider a trip to Tampa, try:
Marine Warehouse Aquarium
8021 W Hillsborough Ave, Tampa, FL 33615
Phone: (813) 884-0787
I have seen a couple of other fair shops in Tampa but don't have the names on me right now.