None is needed to be dosed. If you do regular partial water changes it will replish all your trace elements.
Reef Aquarium Water Parameters by Randy Holmes-Farley - Reefkeeping.com
"I do not presently dose iodine to my aquarium, and do not recommend that others necessarily do so either. Iodine dosing is much more complicated than dosing other ions due to its substantial number of different naturally existing forms, the number of different forms that aquarists actually dose, the fact that all of these forms can interconvert in reef aquaria, and the fact that the available test kits detect only a subset of the total forms present. This complexity, coupled with the fact that no commonly kept reef aquarium species are known to require significant iodine
, suggests that dosing is unnecessary and problematic.
For these reasons, I advise aquarists to NOT try to maintain a specific iodine concentration using supplementation and test kits."