Paranoid of adding fish/coral after ICH outbreak

[ReefKing101]

So after a long wait i managed to iradicate ich from my tank after 11 weeks fallow. I was an idiot who added 2 fish without QT them which is what brought in the ich. So now i'm paranoid of adding anything to the tank fish/coral, i worry that i could be introducing ich. Even if i put fish i buy into a QT and treat them with copper does that still 100% Guarantee no ich?

 

[flampton]

Nothing is guaranteed but qt and treat will increase your odds exponentially