ich on blue morpho

[reefyredfish]

Well, I did the unthinkable and brought a fish home
and put him straight into my display tank. The blue morpho
showed signs of ich almost immediately. Then it looked better
so I left him in there for a week feeding him formula 2 soaked in garlic.
Then my six line wrasse and false perc started to scrape, just a
little bit. They never showed any spots and have not been scraping
for a day or two. However I removed the tang and am now after
a fresh dip QT'ed him. I read where tangs are not good with copper.
Right? So I should use hyposalintiy method? Right?
How long should treat him? I'll keep a close eye on others, but
does anyone think I should just tear down my 75 g now and
get it over with. I do have a wheeler goby that will be impossible to
catch. If I don't see anything on these fish for 6 to 8 weeks can
I assume it's fine and reintroduce the tang?
100 lbs of live rock and a few corals.
Any thought appreciated. Thank you.