I have a Petsmart by me that does an excellent job with their fish husbandry. Tanks are always clean and clear, even their heavily overstocked feeder tanks......which I found out runs off a separate filtration system from all the other tanks.Depend on the location, I love to buy fish from my local Petsmart. Their fish much much healthier than any Chinese, Thai or any Asian fish stores around my area, the down side of Petsmart is that they have very limited fish stock and only carry majority of community fish species. So if I want community fish, the first pet shop i will visit is my local Petsmart, I couldn't pass the 1 dollar deal for on some species. Also, dirty water. sick, dead fish happen in all LFS, you didn't know they were netted out all the dead/sick fishes and fed them to predator species before their store open everyday...That's why many of us here setup an extra tank called "Hospital or quarantine tank" for that reason...
Early last summer, they had a 50% off sale on clown loaches, so I snatched all they had (15). I lost 3 within the first month, but the remaining 12 has more than triple in size. Also around the same period, I picked up a tiny firemouth and irr. shark for about $2. Its been well over a year, and all are doing well.
I'm also a firm believer in QTing everything for about 2 months or more, no matter the source.