Potassium Iodide

[packer]

Who uses this and what are your thoughts. I used Lugols for awhile but only say 1 drop in a 75 gallon tank every few weeks. I was testing and it seems even at this rate I was at the high end. I do run GAC so need input on if the Iodide would be a benefit for me. Trying to get away from the bad parts of iodine via lugols. I have a mixed reef, but only a few LPS and more SPS overall.

[Randy Holmes-Farley]

I do not recommend adding iodine supplements because I believe them to not be beneficial, but if you do use them, potassium iodide is a perfect chemical to use, IMO. Better than Lugols.

I would not dose to maintain a specific level, as iodide is rapidly converted into other forms that may or may not be accounted for by hobby kits.

This article has more:

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

Iodine in Reef Tanks 2: Effects on Macroalgae Growth
http://www.advancedaquarist.com/issu...l2003/chem.htm

and

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 the second one:

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

Supplementing Iodine



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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).

[packer]

Thanks Randy, I have read many of your articles and studies and will follow suit and not dose. Actually I had not for almost a year and then did so slightly as stated for a few months although it has now been about two since I dosed any. Things in my tank are great and that is why I asked. Why change a good thing. I agree also it was quite hard to use/read truly the results on the test kits I had. The only result of good I saw was that my shrimp would molt the day after I added it. I really saw no benefit otherwise, so I will leave it to my water change to re supply what might be missing.

[bertoni]

Shrimps use their shells to sequester toxic elements, and thus shed them. Molting is not necessarily a good sign, since it is quite stressful and dangerous for the animal.

[packer]

Yes, but that is how they grow also. I believe they require a bit of iodide to assist in the molting. They always molt once in awhile, I just found it odd the day after I would add a drop of Lugols, I would find molts. It was as if they were waiting for the "boost". But my SPS are more of a treasure so no I supplement for me anylonger.

[Randy Holmes-Farley]

There is no evidence that shrimp need iodine to grow. I've kept shrimp just fine for many years with no supplemental iodine. It is well known that certain additions make them molt. It is not apparent that that is a positive event.