Here's what you should do: buy a product called "Prazipro." You can usually find it through saltwater fish dealers, not chain stores. It works well without negatively harming fish, live rock, etc. You just have to turn off the skimmer and sterilizer for a week or so. I find it to be the next best thing to copper and it will get rid of ich.
Another word of advice: please get a sterilizer (gamma uv sterilizer). Prevention is always the best medicine. Also, feed fish quality food like "New Life Spectrum" exclusively.