Unfortunately that's about it unless you can find the occasional place tucked into a strip mall.
I'm currently in Harrisburg, and whenever I want to do some serious aquarium shopping, I take the drive down to Lancaster and "That Pet Place". Bout 45 minutes from Harrisburg, but worth it because their livestock section alone is bigger than 2 Petcos put together.
"To know that we know what we know, and that we do not know what we do not know, that is true knowledge." -Confucius