Man, you guys are good. Read through all the posts and checked off pretty much all of them in my head.
Only other one I can think of that isn't Petco/smart around here is Marine Scene out the Dulles Tollroad, but it's all reef stuff.
Other than Pristine, I have been to every store in Maryland that Francine and Richard mentioned (thanks to Richard and Mike on a few). They are worth checking out for different reasons.
Lonny, you're right, we really are very lucky to have so many great stores in the DC area. Seriously, if anyone hasn't been those stores, they're missing out.