I've yet to hear of anyone dosing Iodine, for the most part it should be replenished when you do your water changes. You can test for it, and it'd be interesting to see your results.
My personal observations have been that after almost every water change I've done, I'll always see at least one of my inverts molting. Since iodine is important for their molting, I can only assume that my iodine levels are kept at good levels due to my weekly water changes