These are the main ones I use in order of how much I like them
Skoolz of Fish (downtown Richmond)- Best freshwater in the area in my opinion. Owner is really nice and has really different selection. Weird hours but you should at least visit sometime and check it out
Fish World (Midlothian) - My favorite saltwater store. They don't have much of a selection on site, but if you have a particular fish in mind they're usually able to get it for you
Richmond Aquarium (Midlothian) - They specialize in mostly saltwater, but they do have nice fish from time to time. Make sure you double check the fish before you leave though. Some associates have grabbed the wrong fish and I didn't notice till I got home. Asked for 5 emperor tetra and came home with 2 ETs and 3 black neons.
Azalea Aquarium (between richmond and mechanicsville on route 301) - Kinda dirty hole in the wall and the owner's an a** but most of the other employees are pleasant and fairly knowledgeable. They usually have some more exotic stuff such as rays, pacus, big catfish, big cichlids, etc...They also have other fish that you don't see too often such as black cories and dwarf cories. I've found your experience will vary in there depending on who is working.
Atlantis Aquariums (Henrico) - right next to Patterson Avenue Family Practice. The employees aren't much conversationalists and they don't have much as far as fish, but they have TONS of coral and coral frags. All saltwater. Nice store for reefs, but kinda so-so for anything else.
And of course the various Petcos and Petsmarts. Petcos I check from time to time because they change up their inventory fairly often so you might find something interesting if you're lucky and even luckier if it's in good health and even more lucky if you can track down someone to grab it for you. Petsmart is fairly stable as far as their fish go, they have a few different fish that pop up during one part of the year, but otherwise, fairly ordinary fish you can find anywhere. In most cases the fish I've gotten were in good health.
Apparently some walmarts still carry them, but most of their employees I talk to say they don't anymore because they kept dying (from no employee training on fish care). So if you find one that carries them, be sure they're in good health.