Nuxx, you've got me beat. I thought I had the largest home QT for hyposalinty treatment at 110 gallons for 11 fish. You had a 470 gallon tank! Lol.
reelredfish, hyposalinity at 1.009 will kill your coral. Anything above 1.009 won't kill the ich, so it won't work. Nuxx's tank was new, contained only fish, had dry rock jut put in, and no coral. Instead of removing the coral, you can remove the fish into a QT. A QT does not have to be fancy, even a rubbermaid tub will do.