Mr Homer,
Walmart has been instructed by Quality Pets to feed fish flakes. Puffers do not eat fish flakes. Their diet consists of live or frozen food and crustasions. Even if they did eat flakes, which they do not, flakes are a poor substitute, and do not supply required nutrition.
Salt is another requirement for health, that QP has withheld. At best they throw a cup of aquarium salt in the tank which is dispersed through the filtering system, and lost.
Walmart associates are not instructed in proper handling, and often net and pull puffs out of the tank, where they puff air and die. They sell puffers to impulse buyers with no instructions what so ever, about diet, marine salt, dentistry, fin nipping, or safe handling of a tetrodotoxin species.
I rescued over 300 puffers from Walmart, before I stopped Quality Pets Inc from supplying them in the entire SF Bay Area.