Justlooking,
I have the same problem. I have 72 gal main tank, 29hospital tank. All my fish in 72 gal w/inverts. Purchased royal gramma & put in hopsital tank 10 days. No sign of ich.
Added gramma to main tank and now all my fish have ich. I even feed my fish garlic soaked food and every fish now has ich. I completely understand what you are going though!
Can't do hyposalinity because hospital tank prev. had copper in to treat ich problem i had in the past. If I put inverts in hospital tank, they may die. I can't put all my fish from main tank that live in 72 gal tank, where my biological filitriation is set up, into a 29hospital tank where the tank has little to no biological filtration. I'll get all kinds of ammonia spikes.
UGH!
I have no idea what to do now. The last 6 days I've used a product called 'no ich' and even double dosed. As I stated above, now all my fish have ich. As to what happened here is my idea:
every time I add new fish to my tank, they get ich!
I'm completely at my wits end!
I know i have not helped you but maybe though some of my problems we can learn together....