I have a couple of Petsmarts and Petco's that I visit near me. Also another chain called Pet Supplies Plus.
I've bought fish from them once but it's usually where I go to get my dogs food.
But there is this one small pet store called Slither n Swim that I like. They specialize in hard to find freshwater fish, plants and reptiles.
You see this guy when you enter:
And this one of the oddities they have to offer: