Hi
I was given this bit of information re Gill fluke from a friend who keeps koi. I hope it helps.
Treatment: Most sites will give you an elaborate procedure for treating with harsh chemicals that, in my experience, do more harm than good. I've found a much better way. Go to your local fish store and get something made from copper. I recommend Had A Snail, (pictured below) but medicines like Coppersafe work too. I have found that it will end the almost immediately. It also has no effect on your fish, unlike malachite green and many other antiparasitics, which are extremely hard on them. The only drawback is that you must remove all your invertabrates: The reason it's effective is that it kills ALL invertabrates, from the
ICH parasite to shrimp. Invertabrates include snails, clams, lobsters, crayfish, shrimp, and crabs. Note that you should treat for at least 5 days, as the hatching period of fluke eggs (unaffected by copper meds) varies from 2-4 days depending on the water temperature.
regards
Graham