The parasite lives off its hosts and if it cannot find one dies. It's about a 72 hour cycle. But get everything out ASAP and start the recovery process. Be patient and do not put anything back in for about 3 to 4 weeks. I would stay away from tangs.
LOL, I guess you can say that. But I did do a water change. I was not about to go through another ich epidemic. I actually got the idea from a friend and it worked.
When I first started in the hobby, I started with a 65 gallon tank. I had everything that was needed to maintain a healthy tank( protein skimmer, uv sterilizer). I always kept my water clean and maintained my tank. Just as what was said above tangs are prone to ich. If you are into tangs there...