Protozin is pretty good medication I have used it before, however not all ich can be killed with raising the temperature and salt, there are some more resilliant strains about, I have not long ago had that when heat and salt did not work. You can try esha exit if the protozin does not work (do a waterchange and leave the recomended amount of days as per the manufacturers instructions when changing meds), its a highly affective medication and cured the ich I had in a tank in just 4 days, its also biodegradable so no need for massive water changes.