Thanks for the support guys!! The Jack has Gill Fluke at the moment, he is wild caught so theres no doubt where he got it. He lives in brackish so I think the salt has been keeping parasite numbers low but I think their eggs keep hatching and reinfesting. He is fine at the moment, eating normally, colours fine, no clamped fins, looks like a normal healthy fish apart from the patches of scratching, flashing and twitching, which is obviously the flukes disturbing him. Treating the tank with Praziquantal tabs hopefully I kill all the parasites off!!