So two months my 75g tank has been setup and going strong. The wife was in Cedar Rapids two weekends ago and got a powder brown tang she fell in love with at the petco down there. 2 days later it showed signs of ich
We got a hospital tank going after about the 4th day but it was to late, all of our fish are dead now.
My question going forward is how long or what do I need to do to my tank before adding more fish? I assume water changes, but what else can I do that wont hurt my corals?

My question going forward is how long or what do I need to do to my tank before adding more fish? I assume water changes, but what else can I do that wont hurt my corals?