i only did it for that long because they are corals that have been in my system for quite sometime and I toothbrushed them while in the H2O2, so I figure the less time the better in the iodine since I put the coral through enough stress with the H2O2 dip. You don't have to do the iodine I just figured to do it on top of the H2O2 since I already have it out.