Iodized salt

No, I'm not planning to use table salt in my tank.

As some of you may recall, I acquired my entire marine set-up from a
friend of a friend. Last night, the person in the middle and I were at
a party together, and he mentioned that he had been unable to accept the
set-up because he's sensitive to iodine and, in his words, salt-water
tanks use iodized salt.

Well, as soon as I got home I grabbed my big bag-o-salt and while is
promenently mentions calsium and magnesium, I don't see iodine mentioned
anywhere. OTOH, there's also no mention of anything else in salt. So,
how much iodine is there is marine salt and how does it compare to table
salt? (BTW, this particular person is generally regarded in our circle
of friends as most the likely to make dubious statements.)