There is no such thing as a reef safe medication. You should never treat your display tank - ever!
If a medication is effective it likely kills something you may not want to get killed. And even those "reef safe" remedies that are not effective may have funny side effects you may only find out about when it's too late.
An example of an effective medication which many here deem reef safe is Prazi Pro. But it will surely also kill beneficial worms and flatworms (yes, those exist as well), likely also featherdusters and who knows what else.
The other reason why medicating the display is a bad idea are unwanted side effects that may cause toxicities or render the medication ineffective.
And then there are long-term effect that are hard to pinpoint, just corals not doing as well as before or the like, mysterious fish deaths, ...
Medicating a reef tank: BAD IDEA!