I work at Walmart and it's appalling. I would gladly volunteer to take over fish duties, but for whatever reason they won't allow it. I know at least one other employee would gladly do it, and knows far more about fish care than anyone who is actually "caring" for the fish. Apparently the filter that they run are connected to several tanks. So it's one filter for each row of tanks I think.
So if one tank get's infected, they'd have to treat all the tanks. And they're too lazy. Also, the gravel is just creating problems. It doesn't get vacuumed EVER. It's a poison trap waiting to be sprung. If it were up to me, I'd be pulling the gravel from ALL the tanks. No, it doesn't look as pretty, but the water would be cleaner. I've noticed that the more reliable and quality fish suppliers and breeders with large quantities of fish will not have gravel in their tanks. And then I'd institute water changes on a weekly basis at the very least. More frequently at first because of the current poor water quality and for the overstocked tanks. Daily for the betta fish. And they would all actually get fed everyday. We're hoping that they just quit carrying live fish at all. But people keep coming in and buying them so they keep stocking them.