In my area, as they remodel each Walmart, they eliminate the fish section completely. I was over getting a new starter for my 20g hood and picked up one of their 29g boxed sets for $49 in the clearance area. They also had all of their stresscoat meds in clearance and all other tank sets except for 2 10g are already gone. Salesclerk said that they will not have a fish section at that Walmart in a few weeks. I plan on stopping in and checking a few times a week to see when the rest of the hardware, medicine and food go on clearance.
Also, I bought 3 Pictus cats frrom a Walmart last year and all are still going strong. Not to say that I would buy just any fish from a Walmart, but these cats looked okay and none of the other tanks showed signs of illness, just overcrowding. My son worked at that store and the clerk in the pet center cared about her job. The location I was in yesterday the mollies were sick and so were some parrot cichlids, so it really depends on the store.