Its baaaaaack! Please Read!

[George]

Sorry about your lost.
There must be an explanation as to why your ich re-occurs in your previously fallow tank. From all the scientific paper and numerous expert articles on marine ich, they all say ich needs a fish host during free swimming stage otherwise it will die after a day or two. And the cyst stage of ich is up to 28 days.
If you want to get to the bottom of this, tell us a little bit more about how you QT your harlequin tusk. How long is the copper treatment. Did you test for level of copper during the treatment? How long is the QT period after the copper treatment?