I drove from Arlington, VA to the Baltimore area to see what I could find. I visited 3 locations and didn't like 2 of them. The last stop was House of Tropicals and I made my purchases there.
Another place is Congressional Aquarium in Rockville, MD. They're pretty pricey there but they know their stuff. They have rows and rows of fish. Both freshwater and saltwater. This is my go-to spot for certain things.
There is another place in Silver Spring called Tropical Lagoon Aquarium. I haven't been there yet, although I want to go. I've only spoken to them on the phone when I was trying to get a price on a 10g setup. If you read their reviews, people claim they're great there.
Wet Pets is also another spot in Silver Spring. Never been there either.
Try and find some local fish clubs in the Baltimore area. You'd be surprised what people have to sale or can even point you in the right direction. I've found many breeders by doing a search in my area. Now I have contacts for plants and shrimp. And I get it much cheaper than what I would pay at the store.