Are there any diseases/parasites that cannot be solved with epsom salt and high temperature? (ex: fin rot, tapeworms, hookworms, ick, HITH/hole in the head disease, dropsy, bloat, etc.)
Turning the heat up to 100° is almost guaranteed to kill almost any parasite or pathogen though.Heat actually makes some bacteria more virulent.
Although we use heat to speed up the life cycle of ick, bacteria such as columnaris reproduce faster at water temps above 82'F making the infections worse , more deadly.
When I worked as a microbiologist we used incubators at temps in the 90s to grow pathogens cultures.
So turning up the temp when a fish appears sick is often a death sentence.