IMO the best way I have found to get rid of Ich
1. Hold off adding any new life for at least 10 days. (lifespan of free floating Ich in the water)
2. Install a UV sterilizer to kill any free floating microbacteria associated with Ich as well as other bad stuff. Yes, it can and will kill some of the good bacteria too, but whatever bacteria that is on your LR will remain and should be enough to feed the tank.
3. Using a QT is a good idea but make sure you treat the new livestock while you have them in the QT.
A. I will be treating with copper for 10 days and as well as melafix if the new fish has any types of blemishes. (you can talk the LF dealer down in price if there are blemishes...
)
B. Then I do a 100% water change in the QT and go 10 days without any additives, just allowing the fish to breathe the saltwater and clear any copper and other stuff from it's system.
**NOTE** Make sure you acclimate the fish to the QT each time it goes into it. (during medicine phase as well as saltwater only phase) Also, You dont need to go 10 and 10, that is just my preference. A buddy of mine does 7 days treating with copper, 7 days of saltwater only and melafix if there are any wounds and another 3-7 days of saltwater only.
4. Then the new fish is ready for your display.
5. Finally, you would be best to ID where the Ich came from and avoid repeating the steps that led to it getting into your system.. I found that every time I fed live brine from a local LFS, Ich would be present within 5-7 days after. Now I only use frozen brine. It is a bit more expensive, but some is combined with stuff for the imune systems and some is for the coloring of your fish that feed on it. This is much better than the live brine which has no nutritional value to your fish.
Again, this is just my opinion and what works for me may not work for you. I have seen people do weird a** sh*t and still come away with some awesome looking tanks. They are lucky because they defy all science involved and their tanks never seem to get a "cold." None of this matters if your wife puts about 5-6 fish in the tank while you are at work and then leaves the dead ones in the tank overnight like mine did. It was pretty neat to watch the way the tank goes into a rapid cycle and kills off all the fish only leaving rock, corals and inverts alone.
This hobby seems to be more stressful inducing than stress relieving huh?