How do you know it's not there?
I guess if an expert like Frank Millero can come up with that chemical formula for scientific use, he must figure there is no need to add a form of iodine
Forms of iodine are probably there in the form of "contaminates".
I don't believe in iodine additions even in my reef tanks as the salt water mix already has some in it, and, whenever I feed my tanks, iodine is added to the tanks via that food.
My home made mix is for fish only tanks and hasn't the same needs as the reef tanks.
In 13 years of reefing, I haven't dosed iodine or any other trace element and my tanks haven't suffered for it, fish only or reef.
I don't really understand the concern by some for the addition of iodine, when probably the majority have never used it and had no problems due to not dosing.
Also, I've been unable to locate any documentation of any legitimate study to show that iodine needs to be added to our tanks.