For corals, people do freshwater dips, hydrogen peroxide dips (to remove certain nuisance algaes), pest removing prodcuts like the Coral Rx and others, and then the iodine dips....

I'm about to dip with Lugol's which is a strong iodine dip. To quote the bottle: "Iodine essentially bonds with oxygen to form non-toxic zooxanthellae and enabling the host organism to open fully."