I usually go to the Hidden Reef in Levittown. They post the new stock they get online each week so its easy to see what they get in. There is another store called the fish factory pretty much down the street that I like.
There is also Aquarium center near Deptford NJ. The SW section is small, but I like the FW and dry goods.
Last but not least, is That Fish Place by Lancaster. Cheapest dry goods around and they carry pretty much everything. They sell livestock online and im pretty sure you can order online then go there to pick up. Much cheaper on shipping that way and it also gives you an idea of what they have in sock at the store. Its also a full pet store, like a super walmart for pets

. reptiles section is sweet too.
That Fish Place is worth seeing at least once IMO. However due to the drive if I'm buying livestock I always bring a foam cooler and blankets to insulate the bags and insure the best conditions for my trip back. I have bought FW from there and had no issues with drive time.