heat and salt method has always worked for me on all sick fish i had ( not many sick fish throughout my fishkeeping though )
I'm pretty sure that one of the first things that every single book I have read on fish (which is a lot of them) said was to never buy a fish that is obviously sick in the hopes of saving them. There is no way to tell if these fish will make it, and you'll be out time, resources, and money that you spent trying to treat them. Especially the one with mouth fungus, which can be tricky and even expensive to treat.
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