Walmart is not a specialized pet store. They do not have the expertise to take care of the fish nor they are willing to take good care of their fish. They treat their fish like any other merchandise on their shelves. Most of fish tanks at walmart are quite dirty with plenty of dead fish at the bottom. It is quite a normal scene at any walmart that sells fish. One of the stories I heard was that walmart employees are not allowed to stay in front of their fish tanks for more than a certain period of time each day. Not sure if it was true, but it was a quote from an employee who used to be in charge of the fish there. The time limit put on him did not allow him to properly take care of the fish.
Several years ago there was the rumor that Walmart would be stop selling fish, but I guess it was false.
