i work at petsmart too, as a groomer... we have some very knowledgable staff in my store, and i myself have been learning quite a few things about the fish. we have gravel tanks with some decor, and tanks are scrubbed every week, gravel is siphoned every week, and incompatible fish are never put in the same tank.
i'm rather proud of our store and our employees. now, the petsmart up the street from ours is JUST AWFUL and i would not EVER buy a fish from there. same goes for petco, which, on the whole, has crappy fish that are way too overcrowded and just not very pretty.