I don't have a quarantine, and ffor a year and a half i didnt get ich. I just saw it on my flame Angel and Fire fish. I dealt with Ich alot on my fresh water fish ...and i usually feed them alot and raise the temp. and add stress coat from API.
I have a colony of GSPs, a fire fish , a flame , a pair of false percs, and a mandarin goby on a 32gallon.
The only infected fish i have observed are the flame and fire.
I just raised the temp to 85 and was going to lower at 72 within a day.
And I'll be doing a 30% waterchange after lowering it at 72.