My 100 gallon saltwater tank and just been infested with ICH. I have FOWLR and have been treating the tank with Rid ICH. I didn't have any problems until I introduced a powder blue tang into the tank. About 2 weeks later we have ICH. I have treated once and then did a 25% water change and treated again. The fish look good until about 5pm in the evening when they start breaking out with ICH again. The bottle of Rid ICH say to do a partial water change before each treatment, is this safe? I don't want my newly established tank to go through a mini cycle. It's only been set up for a little over 3 months now. Any suggestions? Will this just run its course and should I continue to use Rid ICH? Please help.