hey welcome to fairfax
theres petcos in the area here are the addresses...
Burke
9230-B Old Keene Mill Road
Burke, VA 22015-4201
703-455-2007
Fairfax
10708 Lee Highway
Fairfax, VA 22030
703-352-3300
there is also a petsmart in fair lakes near centreville but it doesn't sell saltwater livestock.
There is a really good specialty fish store in alexandria called Wally's Aquarium... i would go there to get the best stuff. its about 13 miles from fairfax where i live.