Iodine, Iodate, Iodide....?

[IanF]

My toadstool mushroom as been looking very pale for the last week or so - the polyps are still out, although not at their best. The tank,s about 14 months old, and the coral has been in and doing very well for the last year.

I did some searching on the potential causes, and read that this may be a symptom of iodine deficiency - causing bleaching. Up until now I haven't been dosing iodine - I've only the one coral, so I've been relying on water changes to maintain levels (about 8% changed per week).

However, with the sick looking coral I invested in a Salifert I2 test kit.

Running both the iodide and iodate tests, I get the following results:

Iodide: 0.04 (which I believe is OK)
Iodate: zero

The iodine additives I've looked at seem to be iodide based, buit do say that the different forms of iodine convert beween themselves.

If I add sometthing like the Kent Marine Iodine suppliment, will this bring the Iodate values back up to target - and will this help my coral?

Thanks in advance - Happy Christmas to those that believe in that sort of thing!

Ian


Other tank parameters:
pH 8.3
KH 8.9
NO2 0
NO3 2.0
SG 1.024
Rowaphos in tank, but no carbon
Deltec skimmer

 

[sothoth]

The form of iodine you have is related to the pH of your system. At pH 8ish (which is what you want and what you've got) you should have it in the iodide form, which is I-. Its formed when iodine (I2) reacts with water at alkali pH and breaks down. I- is the good stuff, which is taken up by your inverts and fish.

Iodate forms from iodine when the pH is low (acidic, <7) so you should have very little at your pH, if any. This is also good since you don't seem to have any. For anyone who cares about the chemistry, Iodate is the salt form of iodic acid, so iodic acid turns to iodate salts when it reacts with potassium, calcium, etc. You don't really want that in your tank since its presence is indicitave of too low a dangerously low pH and will bind to good stuff (like calcium) that you want to be free and not tied up in iodate.

I don't know for sure about your toadstool but I don't think the iodine has anything to do with it.

I've only kept a toadstool once and it did great. I found that it liked low-ish current, and fairly bright light. It also ate a lot, so I fed the tank filter feeder food regularly. Mine flourished under those conditions.

They DO shed occasionally, and they look kind of bad right after, so I'm hoping that's what you're seeing and it will go away in a few days. Usually mine would look like a million dollars after I waited for it's post-shed slump to go away.

Hope this helps.

 

[IanF]

Thanks for the brilliant response. I'll ignore the iodine red herring, and look for alternative reasons for my sick mushroom.

It's been through several shed/recover cycles since I've had it, so I don't think it's that. However I have just increased the water flow rate with a couple of new powerheads - maybe it's too vigourous for it in the current (excuse the pun!) location.

Ian

 

[steelhealr]

Don't dose your tank with iodine.

http/www.fishforums.net/index.php?showto...0&hl=iodine

SH

 

[sothoth]

oops

 

[sothoth]

Don't dose your tank with iodine.

I don't want to get into the debate about whether you should dose with iodine or not, but I want to clarify a point that while iodate is the prevalent form in the ocean that's not the case in surface waters (like reefs) where iodide is more dominant.

But, I think I was rash by saying its pH dependant, I read a few things that suggests no one really knows why iodate isn't as prevalent in surface waters but some have suggested that marine life absorbs some forms more than others and leaves the ocean water more depleted, among other explanations. It seems to be an area of fierce debate among oceanography people.

Sorry for the info on pH if it was incorrect, I'm not sure I gave the right explanation so either I'm really wrong or I'm lucky and guessed right.

I think the most important point, though, is that the ocean dynamics of iodine oxidation and reduction may have little in common with what you see in your tank. I'd still predict iodate is less common in your tank due to it being more like surface water (little iodate) than deeper water (more iodate).