Real salt for me is salt with 60 + trace minerals in it.
Salt water aquarium fish would float on top pretty soon if to swim in table salt ed water, while they thrive in "real" salt water. The 2 % of minerals seems to do the difference.
All over the world one can get Iodine / Lugols in aquarium shops, as it is essential to their health. If all other source of purchasing Iodine are put down, we can always rely on the aquarium shops.