Iodine
Naturally exists as:
I
-
iodide
(0.01 0.02 ppm)
IO
3
-
iodate
(0.04 0.06 ppm)
Organic Iodine such as methyl iodide
What uses it?
Corals (gorgonia, black corals, soft corals)
Trunicates, sponges, worms, shrimp
Algae