-cough- Being probably the only decent walmart fish department employee on this planet (ok im sure there are a few more of us) I do use Melafix for my fish if we have any that look like they have fin damage. In fact the store supplies it along with salt and a few other bottles of this and that.
But having to treat fin damage is a rarity in our store since we do almost daily water changes (at *least* twice a week). Sometimes we get fish that come from our supplier with damaged fins which is beyond irratating but they are given as much TLC as we can at the store.
It's just sad that most Walmarts do not make a point to hire knowledgable people for their fish/pet departments. My store was smart and hired me along with my supervisor who is also a big fish keeper, breeder and betta hobbiest.
But you guys are right, many Walmarts make me sick in their ####ty attempts at running an aquarium. I can only stick up for my store because I know whats being done "behind the scenes" and I personally, truely care for those fish. But other stores; hmph. They are on their own in trying to justify the toliet bowls of death they supply their fish with.