Iodine - Let's collect what we know.

[dannybradley]

This should be wiki material.

There are many forms of iodine that we deal with in aquariums. Some supplements are the same, while some vary radically, and others are unsutible for use inside the aquarium. This post will focus mainly on I-(iodide, sold as potassium iodide KI) because it is the form that is actually utilized by coral life. The sum concentration of I2(iodine), I-(iodide), IO3-(iodate).

We all know invertebrates use iodine during molting, but what else does it benefit? Coral uses iodide to assist in the expulsion of excess O2 caused by over active zooxanthella. They uptake I- to convert it to IO3-, which they then release back into the water column.

3O2 + 2I- -> 2IO3-

According to Seachem, KIO3 release the O3 at a pH at or above 8.3 at a very slow rate. You'll understand why that's important to know once I get into product description.

Chris Brightwell in his book Marine Chemistry states, "Iodine may very well be one of the most important elements present in a reef aquarium; its concentration is usually a limiting factor in the rate of metabolism and growth of fishes and invertebrates." He goes on to describe many other ill effects of a lack of iodine.

Iodine can wreck havoc in a system if overdosed and can magnify the growth of cyanobacteria if phosphate and nitrate are not controlled.


So what do they put in those bottles and which one is right for me?

We'll start with my favorite:
Seachem Reef Iodide - KI(potassium iodide). It's very bioavailible as it's in the form that the corals need. It is quickly untilized and should be dosed in small quantities several times a week.

Kent Concentrated Iodine: I2 and KI. I'm not sure as to why Kent included elemental iodide in this blend. It may be because it is double concentration. I2 will become I- in the aquarium, but at a slow rate.

Kent Tech I - timed release proprietary concentrated iodide, I2, KI. Kent's secret iodine receipe! The secret ingredient is IO3-. The premis of this product is a time released iodine supplement that provides for a constant level of iodine, whereas Seachem Iodide will cause spikes. IO3- and I2 both will form I- in the aquarium, but at different rates. This slow breakdown is the secret behind the formula. It's a neat idea, but the concentration is very low. It's dosed 3 times a week at a rate of 5mL/20g of water. This makes it very hard to dose a large tank. Another issue is that a U.V. will cause IO3- and I2 to break down into I- very rapidly, causing a huge increase in I-.

Lugul's Solution- KI, I2. The same as Kent's Concentrated Iodine, except this one really is VERY concentrated. It is dosed at a rate of one drop/25g.

All iodine products on the market are basically going to be a blend or single of I2, I-, and IO3- or just one of the 3, based on the culture and beliefs of the company producing it. I'm sure there's plenty I haven't listed here about iodine, but I hope this helps. Address anything I may have wrong here or ask a question if you need some clarification.

 

[cameron]

We all know invertebrates use iodine during molting, but what else does it benefit?

I think Randy Holmes-Farley disagrees with this point. No one has proven to my knowledge that dosed iodine or iodide do anything in the molting process, growth of xenia or algae. They know it is found in these animals but again in my research I haven't found anyone who has actually done a study proving how much or why you even need it.

From the horses mouth so to speak:

http://www.advancedaquarist.com/issues/mar2003/chem.htm">[B]<span style="color: #810081;">Iodine</span>[/B]</a>
I do not presently dose iodine to my aquarium, and do not recommend that others necessarily 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.

[B]For these reasons, I advise aquarists to NOT try to maintain a specific iodine concentration using supplementation and test kits. [/B]
Iodine in the ocean exists in a [IMG]http://www.advancedaquarist.com/issues/mar2003/chem.htm"><span style="color: #810081;">wide variety of forms</span></a>, both organic and inorganic, and the iodine cycles between these various compounds are very complex and are still an area of active research. The nature of inorganic iodine in the oceans has been generally known for decades. The two predominate forms are iodate (IO<span style="font-size: 1-1px;">3-</span>) and iodide (I<span style="font-size: 1-1px;">-</span>). Together these two iodine species usually add up to about 0.06 ppm total iodine, but the reported values vary by a factor of about two. In surface seawater, iodate usually dominates, with typical values in the range of 0.04 to 0.06 ppm iodine. Likewise, iodide is usually present at lower concentrations, typically 0.01 to 0.02 ppm iodine.

[IMG]http://www.advancedaquarist.com/issues/mar2003/chem.htm"><span style="color: #810081;">Organic forms of iodine</span></a> are any in which the iodine atom is covalently attached to a carbon atom, such as methyl iodide, CH<span style="font-size: 1-1px;">3</span>I. The concentrations of these organic forms (of which there are many different molecules) are only now becoming recognized by oceanographers. In some coastal areas, organic forms can comprise up to 40% of the total iodine, so many previous reports of negligible levels of organoiodine compounds may be incorrect.
The primary organisms in reef aquaria that "use" iodine, at least as far as are known in the scientific literature, are algae (both micro and macro). [IMG]http://www.advancedaquarist.com/issues/april2003/chem.htm"><span style="color: #810081;">My experiments</span></a> with [I]Caulerpa racemosa</em> and [I]Chaetomorpha</em> sp. suggest that iodide additions do not increase the growth rate of these macroalgae, which are commonly used in refugia.

Finally, for those interested in dosing iodine, I suggest that [IMG]http://www.advancedaquarist.com/issues/mar2003/chem.htm"><span style="color: #810081;">iodide</span></a> is the most appropriate form for dosing. Iodide is more readily used by some organisms than is iodate, and it is detected by both currently available iodine test kits (Seachem and Salifert). [/QUOTE]

[IMG]http://reefkeeping.com/issues/2004-05/rhf/index.php">http://reefkeeping.com/issues/2004-05/rhf/index.php</a>

He even did studies with algae and basically showed no real proof either way iodine supplemenation does anything at all. I have read a couple of other studies that back this up and I will see if I can dig them up.

Panda might have something to say about this as well. He often reads up more than I do on this type of stuff.

 

[cameron]

To add to this, I have at least 6 large shrimp and I have not dosed any form of iodide, iodine or iodate in well over 8 months. Several moltings and no deaths so far.

 

[dannybradley]

The simple answer is that we really have no clue, but we may be able to come to a reasonable opinion if we put our heads together on this one.

When you're using it as a dip it's acting as an antiseptic. You're using it in hopes that it will kill whatever is bothering the organism. Chris Brightwell goes on to state that iodine is very important, specifically for leathers. I don't have the book in front of me, so I'll type up some of that chapter tomorrow.

One thing I would keep in mind. In the aquarium we typically keep levels at higher concentrations than NSW to assure that there's never a lack thereof. Some study down the road may prove that this incorrect. From my personal experience, and take into account I prefer softie and LPS, a dosed tank does get better and fuller growth than an undosed tank. This is broad spectrum dosing, however.

Although iodine does cycle between many forms it is still depleted by skimming, ozone, carbon, etc. I'm sure you can have a successful tank by not dosing, just as you can have a success at with a Ca level of 380ppm. You may, however, have more success if you're able to identify that your tank has a defincincy in iodine. Touch and Go testing is certainly not the best advice I can give, but it's all hobbiest have sometimes.

 

[cameron]

DannyBradley;112955 wrote: Chris Brightwell goes on to state that iodine is very important, specifically for leathers. I don't have the book in front of me, so I'll type up some of that chapter tomorrow.

One thing I would keep in mind. In the aquarium we typically keep levels at higher concentrations than NSW to assure that there's never a lack thereof. Some study down the road may prove that this incorrect. From my personal experience, and take into account I prefer softie and LPS, a dosed tank does get better and fuller growth than an undosed tank. This is broad spectrum dosing, however.

I gotta pull a Panda on this one... I need to see proof. Observation without a control is simply not good enough to justify dosing a chemical IMO. Especailly one that nobody I have found can actually show how an animal or plant pulls it from the water column. For all I know they get the bulk of their supplementation from feeding which means dosing Iod???? in any form is a waste of money (this is my personal belief BTW from the reading I have done on the subject). The longer I am in this hobby the more I believe there are a lot of companies that sell snake oil and this one easily could be top of the list. It is a two-for with the dosing on one side and the kit to test on the other.

Another Holmes-Farley discussion on the subject where he goes down the list of creatures and pretty much casts doubt on the "hard science" of dosing for each critter: http://www.advancedaquarist.com/issues/mar2003/chem.htm">http://www.advancedaquarist.com/issues/mar2003/chem.htm</a>

[QUOTE=][B]DannyBradley;112955 wrote:[/B] Although iodine does cycle between many forms it is still depleted by skimming, ozone, carbon, etc. I'm sure you can have a successful tank by not dosing, just as you can have a success at with a Ca level of 380ppm. You may, however, have more success if you're able to identify that your tank has a defincincy in iodine. Touch and Go testing is certainly not the best advice I can give, but it's all hobbiest have sometimes.[/QUOTE]Sheer speculation... Iodine has very little in common with Calcium. We know exactly what calcium is, how it is sustained in the water column and how it is used by corals and other critters. We have very little understanding about the various forms of iod???? and how corals extract/use it or even how to reliably test for it. Barring heavy water changes, I seriously doubt an SPS tank could go 8 months without calcium supplementation and not have some serious issues. I am sure that a tank can go 8-10 months hell 5 years without dosing iod???? and I doubt it will have any serious consequences on the softies, inverts, etc and possibly no consequences at all. Given what we know today, they could actually do better.

I don't think there is anything wrong with someone dosing it carefully as it MIGHT do something positive (and I think just as likely does something negative but that is IMO), but I don't like that companies prattle off about the need for iod???? when they have no independant studies or proof their product even does what they claim it does. The way these companies sell their stuff is amazing. Makes me want to take a crap, bottle it up and sell it is processed softie supplementation. I could even sell a kit and not tell anyone how it works or produce a study backing me up. I guarantee I will be able to find a horde of consumers who swear by it.

So my opinion and only my opinion... water changes and feeding get the job done and I will stand by that until some people publish a study showing the benefits and not just some half-arsed speculation from someone selling the stuff either.

 

[jaandgc]

Cameron, only 4 more post to make 4000.

 

[cameron]

Hadn't even noticed. Scary part is a took a break for a couple months where I was posting only a couple times per week. Man can I talk... err... type or what?

 

[dannybradley]

I completly agree with you on that we need some hard studies backing this up, but when there are no hard studies to examine, we have to take into account what we do have, which is the sheer volume of anecdotal evidence of the benefit of dosing iodine. I do say that with much reluctance, however.

Not everyone has the same results from dosing it simply because no two people care for their tank the same way nor do they have the same stock. A tank that is not deficient in iodine will not benefit from dosing, whereas one that is will obviously benefit.

The only way it should be dosed, and this is where we actually agree on something completly, is extremely moderatly and only in the form of KI, until we actually know something more.

There are plenty of snake oil products out there, but there is eveidence that I- is utilized by coral.

 

[cameron]

I can't find any evidence that dosed Iod???? is actively consumed in the water column by corals and livestock nor can I find any evidence that it is used by most corals. They know corals like xenia have concentrations of it but have no idea what it does or how it gets there. Plus you can't really accurately measure iod???? as none of the tests account for the dozens of forms it takes in aquaria. You could have a very high x iod???? and be dosing doing nothing but harm. My question is why dose soemthing when there is no imperical evidence it does something and you have no way of really measuring its effects? Especially something as potentially dangerous as iodide. It is kinda like people dumping HGH in their tanks... I don't get that either but a lot of people swear by it.

Just my opinion though. I know a lot of people dose it because they are trying to get NSW levels, but like Holmes-Farley I just think it is too difficult if not impossible to do currently and nobody knows the benefits at least not proven from what I have seen.

 

[dannybradley]

If there are a dozen or some different forms of iodine present in saltwater you can't argue that they're all doing the same thing. I4O9 Iodine Oxide is going to havecompletely different chemical properties than I- . It's like saying because there's hydrogen in H20, we should be really careful about putting water into our tanks because of the hydrogen. I know this is an extreme example, but you can see where I'm coming from.

As far as nobody knowing the benefits, Chris Brightwell makes some compelling arguements. I'll have to get his book into your hands.

 

[cameron]

You are kinda making my point for me. There are a rather large variety of iodine sources in the tank and the way most people dose only effects one of them, the tests only measure a small subset (mainly the kind you dose), nobody seems to know which one what creature uses and how each form is beneficial/harmful/useless. Besides, my issue isn't the different properties and forms of iod???? it is the fact that nobody seems to know how lifeforms in our tanks actually use them. Dosing the way some do may be completely useless, it might help or it could even inhibit growth/coloration of several species... nobody seems to know the answer because the research doesn't seem to be there. The only research I have found seems to indicate that food is the primary source for virtually all iodine found in shrimp and crabs. I haven't been able to find zip on xenia. I have found no research that explains how iodine is used by these lifeforms. People seem to know iodine collects in xenia but how it gets there, what it is used for and even if it is beneficial seems a mystery.

I am all for reading more on the subject and I haven't read Brightwell's book (and I will soon) but to date every author I have read that recommends the stuff doesn't have any real science backing them up. They make the leap that iod???? in the water column is important because it is also found in the lifeform. That is a HUGE leap IMO.

Where is Panda anyway? I am interested to get his skeptical opinion.