First of all, I apologize if wasn't very clear from the beginning about why I did the FW dip. I did this in an effort to rid the frogspawn of some flatworms I saw that may have been agitating my coral. Some flatworms have no ill effects, and still others do. First you have to identify if the need for a FW dip is present. From my particular view, it was because I clearly saw flatworms on my coral, and not wanting to use anything too aggressive like a medication (since my coral was already to it's brink) I found that fresh water (preferably some RODI) will kill salt water worms. For some severe cases of flat worms there is flatworm-x that is arguably safe and effective for reef tanks, but I'm glad my particular dealing was focused on just my frogspawn. To answer your question more directly, a fresh water dip will not medicate your coral. It will simply rid it of any known parasites it has. But, you must first identify the cause of what is harming the organism first. Different corals react differently to this treatment, and I was warned that frogspawn don't particularly like this method. But, if used sparingly, it can be a good treatment.