Well it is a way to treat sick fish, I have used as a last resort. Some people do a fresh water dip on all new fish in hopes of preventing flukes and ich and other bad stuff from entering tank. However ich has been proven to be in just about any tank and is part of a balance reef in nature. (balanced does not mean causing disease)

The way I have done it is to take R/O and used a buffer to bring pH to the range of your tank. Make sure temperature is close also. Place fish in water,(would have to read what time people suggest) remove fish after a brief dip and hope you killed the bad guys. I saved a tang one time with this that had developed a bad case of flukes after my cleaner shrimp died. I have also lost fish after doing this too. I might use it early if I was for sure flukes where the problem. Just keep a cleaner shrimp and you don't have to worry about that.

Hope that helps,

Mike