It's been impossible (in the last couple years) to find and buy medicated food to save fish with bacterial infections but now there are easy ways to make such food successfully.
It helps to forge a relationship with a legitimate veterinarian who can prescribe antimicrobials, but that's not always available. Weekend card table shot-clinic-vets are "special" in that they aren't regulated by laws that pertain to brick and mortar vets. For example they don't have to have a license to practice in your town or location. They can legally prescribe drugs for a pet they gave shots to one weekend at a feed store, and will never see again. So they have a lot of privileges granted by the FDA and the local VMA's – – that your regular vet can't compete with. So they can be enlisted. But you can also get antibiotics online as long as it has a picture of a fish on the label – apparently that makes it legal to sell antibiotics over the counter without a prescription. Resources are listed in the article I'm referencing here.
The idea is that you can use edible shellac (confectioner's glaze) and bind the medications to the pellet of the appropriate size and kind. And it doesn't float off in the water the way the old old-binding methods did.