Of all the trace elements found in natural sea water, iodine is associated with the widest range of effects. Iodine prevents goiter as an important component of the thyroid hormone. It also is essential for the hardening of the chitinous exoskeleton of crustaceans. Coralline red algae deposit iodine in surface structures and gorgoniias deposit it in the axial skeleton.

The natural replenishment with trace elements is not guaranteed in a saltwater aquarium, iodine should be added to a marine aquarium on a regular basis. Experiments clearly show that Tropic Marin® IOD improves the adaptation to light and the coloring of anthozoa, especially of hard corals. Tropic Marin® IOD contains iodine in its most effective form, as elementary I2in a Lugol´s solution.