I have had to treat crytocaryon and amyloodinium on quite a few fish. I think copper at the proper dose is the best cure if you can do it. but sometimes you just don't have the time or resources. If it is just marine ich or crytocaryon i have just left the fish in the main tank and fed spirullina enriched brine and formula pellets and 95% of the time it will just go away as long as you have a healthy tank and good water parameters. I also do daily water changes.