JennM;1005246 wrote: Stress Coat and Melafix are crap (sorry, Jeff...).
Post some pictures, we might be able to identify what it is. If it's Oodinium or Amyloodinium, if you aren't treating it with real medicine, the fish will be dead soon (if it isn't already).
Why on earth would you buy a sick fish? Or why would a store sell it? If a store isn't willing to treat a sick fish, you should rethink patronizing that store, in my opinion.
Jenn