The different between iodine and lugols ! [Archive]

Randy Holmes-Farley

12/11/2008, 09:11 AM

I detail the different forms here:

Iodine in Marine Aquaria: Part I
http://www.advancedaquarist.com/issues/mar2003/chem.htm

FWIW, I generally do not consider dosing iodine to be useful, except perhaps for certain gorgonia that are known to use iodine. I discuss that here:

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented
http://reefkeeping.com/issues/2007-04/rhf/index.php

from it:

http://reefkeeping.com/issues/2007-04/rhf/index.php#17

Supplementing Iodine
Many aquarists dose iodine, and claim that certain organisms need it to thrive. Often mentioned are shrimp, Xenia species of soft corals, mushroom corals, and more. However, no evidence for an iodine requirement by these organisms appears anywhere in the scientific literature. They also thrive quite well in many coral reef aquaria where iodine is not dosed. Of Reef Central’s Tanks of the Month for the past couple of years, the majority do not supplement with any form of iodine (or at least do not mention doing so), although some certainly do dose it.

I do not presently dose iodine to my aquarium, and I do not recommend that others do so, either. Iodine dosing is much more complicated than dosing other ions due to its substantial number of different naturally existing forms, the number of different forms that aquarists actually dose, the fact that all of these forms can interconvert in reef aquaria, and the fact that the available test kits detect only a subset of the total forms present. This complexity, coupled with the fact that no commonly kept reef aquarium species are known to require significant iodine, suggests that dosing is unnecessary and problematic. On the other hand, it is nevertheless possible that some organisms that we keep do actually benefit from iodine, and that in some aquaria there is not enough in the foods that we add so that supplements may possibly be beneficial in those aquaria.

I dosed iodine for several years when I first set up my aquarium. I dosed substantial amounts of iodide to try to maintain 0.02 to 0.04 ppm of iodide (which is a natural level). Iodide is rapidly depleted as algae and perhaps other organisms take it up and convert it into organic forms. After a few years of dosing iodide, I became frustrated with the complexities of testing for it, so at that point I stopped dosing any supplemental iodine. That was about seven years ago. I detected no changes in any organisms, and never dosed any again. If you are dosing iodine now, I suggest stopping for a month or two, and seeing if you can objectively detect any difference in any organism.

For these reasons, I especially advise aquarists NOT to try to maintain a specific iodine concentration using supplementation and test kits. For those who do supplement iodine, I suggest iodide as a more suitable form than certain other additives, such as Lugol’s iodine, which is unnatural and potentially more toxic. Iodide is also more readily used than iodate by some organisms, and iodide is detected by both currently available iodine test kits (Seachem and Salifert).