Well, last night I dropped a bomb on my dinos.
I drained the 10g tank that all my old coral and some rock was in, took around 20 seconds or so. I then filled the entire tank with straight RO/DI water. Took me about a minute to fill it up from the water jugs I had so I didn't splash too much lol. After it was full, I timed a full minute. After that, drained the tank again about 20 seconds. Lastly I filled it back up with new saltwater. So the rocks at the bottom of the tank got almost two minutes of freshwater exposure, stuff at the top got a little over one.
Hopefully this punches them in the face! The corals looked good this morning (the lights don't come on til 11AM), so hoping for the best