High Iodine

[CodyF.]

Just received an ICP. I was starting to have STN and after loosing multiple colonies I decided to send in a test. I used ATI-OSE and the results have me puzzled.

In addition to high salinity, I have high iodine. It’s literally like 4 times the amount in natural see water. I don’t dose iodine? I use tropic Marin pro reef salt and AFR.

Any idea where the iodine can be coming from? I feed frozen food.

 

[tripdad]

Hmmmm, interesting. I recently got my test back and had high iodine(very) and high zinc. I am still trying run down the source of both. Forgot to mention I use IO salt and dose AFR

 

[Jamie814]

AFR contains Iodine, 1000ml bottle contains 34 mg based on my research...

"In addition, all essential trace elements are also included: Iodine, bromine and fluorine for the growth and strengthening of skeletons in gorgonian corals, sponges and crabs; selenium for eliminating free radicals, and iron, manganese, zinc, copper, nickel, chromium, cobalt, molybdenum and vanadium for the development of important enzyme complexes."

 

[Randy Holmes-Farley]

I would not attribute the problems to that iodine level.

Was your phosphate high? There can be cross interference..

 

[tripdad]

I would not attribute the problems to that iodine level.

Was your phosphate high? There can be cross interference..

Please expound...

 

[CodyF.]

I would not attribute the problems to that iodine level.

Was your phosphate high? There can be cross interference..

Randy, my phosphates were at .12 according to the ICP. I didn’t do a water change for about two weeks before sending off the ICP. On my Hannah it was about a .10 or so. So no, phosphates were not really high. Higher than I like, but within range.

As you may remember from my previous post, salinity was high though. I ordered the TM hydrometer you recommended.

I did however, find iodine in a food I’ve been feeding. Maybe that is the culprit?

 

[Randy Holmes-Farley]

Randy, my phosphates were at .12 according to the ICP. I didn’t do a water change for about two weeks before sending off the ICP. On my Hannah it was about a .10 or so. So no, phosphates were not really high. Higher than I like, but within range.

As you may remember from my previous post, salinity was high though. I ordered the TM hydrometer you recommended.

I did however, find iodine in a food I’ve been feeding. Maybe that is the culprit?

Maybe. Was it a listed ingredient or just an analysis result? All foods will contain iodine, but not all add extra to it. I personally would not act on that iodine level except maybe not add it so using a different foods seems fine.

 

[CodyF.]

Randy, my phosphates were at .12 according to the ICP. I didn’t do a water change for about two weeks before sending off the ICP. On my Hannah it was about a .10 or so. So no, phosphates were not really high. Higher than I like, but within range.

As you may remember from my previous post, salinity was high though. I ordered the TM hydrometer you recommended.

I did however, find iodine in a food I’ve been feeding. Maybe that is the culprit?

Maybe. Was it a listed ingredient or just an analysis result? All foods will contain iodine, but not all add extra to it. I personally would not act on that iodine level except maybe not add it so using a different foods seems fine.

It’s was listed as an ingredient. I’ve read a few high iodine articles on R2R. In almost all of them you don’t seem concerned with ammonia. Why? Why is 4 times the ammonia not concerning? I’d like to understand deeper.

 

[Randy Holmes-Farley]

It’s was listed as an ingredient. I’ve read a few high iodine articles on R2R. In almost all of them you don’t seem concerned with ammonia. Why? Why is 4 times the ammonia not concerning? I’d like to understand deeper.

Ammonia? What are you referring to?

 

[azreefer93]

I have recent STN event due to high Iodine (at least I didn't figured out other reason). I was dosing AFR and heavy on Nori feeding. I do ICP monthly, the Iodine start creeping up when I switched from Reef Fusion to AFR on Aug 2025 along with half sheet of Nori daily to my 80 gallon tank. So I believe both of these factors contribute to the Iodine level. It was peak 160mgl on Jan 2026, STN events on 3 colonies started a week before Jan 2026's ICP test. To combat this, I switched to Balling A B C with max dose of Tropic Marin K (6ml), half dose of Tropic Marine A (3ml - because this contain Iodine), also cut off Nori feeding (half sheet twice per week). The iodine now backing down to 90mgl on the latest ICP.

Tank is 90% acro, 10% lps, no softy. Params:
SG 1.026
8.2 ALK, 420 Ca, 1340 Mg tested daily
3-5 NO3, 0.09-0.1 PO4 tested daily

 

[Randy Holmes-Farley]

FWIW, I'm skeptical of problems blamed on somewhat elevated iodine. It may be true, but I have seen many people report substantial elevations or dosing overdoses with no problems, and I don't really understand what mechanism would cause a problem.

There are a large number of coral problems that people never understand, and often I suspect those are due to bacteria. Looking at a chemical test and picking out the only thing "wrong" does not necessarily properly finger the culprit.

 

[CodyF.]

It’s was listed as an ingredient. I’ve read a few high iodine articles on R2R. In almost all of them you don’t seem concerned with ammonia. Why? Why is 4 times the ammonia not concerning? I’d like to understand deeper.

Ammonia? What are you referring to?

Yes, sorry. Ammonia. From previous posts I’ve read, you don’t seem to be concerned with high ammonia.

 

[CodyF.]

I have recent STN event due to high Iodine (at least I didn't figured out other reason). I was dosing AFR and heavy on Nori feeding. I do ICP monthly, the Iodine start creeping up when I switched from Reef Fusion to AFR on Aug 2025 along with half sheet of Nori daily to my 80 gallon tank. So I believe both of these factors contribute to the Iodine level. It was peak 160mgl on Jan 2026, STN events on 3 colonies started a week before this ICP test. To combat this, I switched to Balling A B C with max dose of Tropic Marin K (6ml), half dose of Tropic Marine A (3ml - because this contain Iodine), also cut off Nori feeding (half sheet twice per week). The iodine now backing down to 90mgl on the latest ICP.

Tank is 90% acro, 10% lps, no softy. Params:
SG 1.026
8.2 ALK, 420 Ca, 1340 Mg tested daily
3-5 NO3, 0.09-0.1 PO4 tested daily

Do you think the AFR is high in iodine? I’ve been exclusively TM salt and AFR over the last few months. You think the seaweed could have attributed?

I’ve fed nori for a while without issue. It’s either food or AFR/TM salt in my head. For my situation at least.

 

[BryanM]

Do you think the AFR is high in iodine? I’ve been exclusively TM salt and AFR over the last few months. You think the seaweed could have attributed?

I’ve fed nori for a while without issue. It’s either food or AFR/TM salt in my head. For my situation at least.

I dosed AFR for over a year with low iodine ICP test results.... So that's not it.

 

[CodyF.]

FWIW, I'm skeptical of problems blamed on somewhat elevated iodine. It may be true, but I have seen many people report substantial elevations or dosing overdoses with no problems, and I don't really understand what mechanism would cause a problem.

There are a large number of coral problems that people never understand, and often I suspect those are due to bacteria. Looking at a chemical test and picking out the only thing "wrong" does not necessarily properly finger the culprit.

I think I have multiple issues that led to my STN. But, ultimately it drove me to an ICP. I’ve never had high ammonia. But from what I read it was a death sentence until I started reading your inputs. Now I’m curious.

 

[CodyF.]

Do you think the AFR is high in iodine? I’ve been exclusively TM salt and AFR over the last few months. You think the seaweed could have attributed?

I’ve fed nori for a while without issue. It’s either food or AFR/TM salt in my head. For my situation at least.

I dosed AFR for over a year with low iodine ICP test results.... So that's not it.

I would agree. I’ve asked a few respectable people on here before I made the switch to AFR. I heard some bad about it. But, there was a lot of people here that said otherwise.

 

[azreefer93]

Do you think the AFR is high in iodine? I’ve been exclusively TM salt and AFR over the last few months. You think the seaweed could have attributed?

I’ve fed nori for a while without issue. It’s either food or AFR/TM salt in my head. For my situation at least.

I know Tropic Marin increased Iodine recently to their AFR or TM A, I can't remember exactly but I lean on the side that I feed too much Nori. Other thought is Iodine is not being consumped that much in my tank as well so that's why it adding up over time. What is your tank volumne/params? What are you feeding? How much AFR you dose? What is the water change schedule looks like?

 

[Randy Holmes-Farley]

Yes, sorry. Ammonia. From previous posts I’ve read, you don’t seem to be concerned with high ammonia.

I am concerned about high ammonia. Like 5-10 ppm. It takes more than 10 ppm ammonia to kill a typical fish.

I am not concerned about low levels, and I and many others dose ammonia at low levels to boost corals that want ammonia. Companies selling ammonia reduction "products" have conditioned people to be afraid of even safe levels of ammonia.

This has much more, including all of the published tox data I could fine

Ammonia is Our Friend!

Ammonia is Our Friend By Randy Holmes-Farley Yes, I know the title is provocative, and likely goes against much of what you read and hear in the reef aquarium hobby. I believe, however, that the hobby may have been harmed by the continual...

www.reef2reef.com

 

[CodyF.]

Do you think the AFR is high in iodine? I’ve been exclusively TM salt and AFR over the last few months. You think the seaweed could have attributed?

I’ve fed nori for a while without issue. It’s either food or AFR/TM salt in my head. For my situation at least.

I know Tropic Marin increased Iodine recently to their AFR or TM A, I can't remember exactly but I lean on the side that I feed too much Nori. Other thought is Iodine is not being consumped that much in my tank as well so that's why it adding up over time. What is your tank volumne/params? What are you feeding? How much AFR you dose? What is the water change schedule looks like?

My tank is a 50 gallon sps tank. I feed a mixed frozen, krill, fish eggs and a carnivore blend that has iodine added. Noticed last night. I also feed nori. I have 3 angels and a tang.

I’m currently dosing 45 mils of AFR, which has my ALK at about 9.5. A little high for me, but growth has slowed over the last few weeks/months.

Water change weekly, 4gallons. When this ICP was taken, it was two weeks without a water change due to low nutrients.

Alk- 9.5
No3- below 10
Po4 - 1.2 per ICP
Salinity is very high, 1.029-1.030

Slowly lowering it daily. Removing saltwater and adding freshwater. Waiting on a TM hydrometer

 

[azreefer93]

FWIW, I'm skeptical of problems blamed on somewhat elevated iodine. It may be true, but I have seen many people report substantial elevations or dosing overdoses with no problems, and I don't really understand what mechanism would cause a problem.

There are a large number of coral problems that people never understand, and often I suspect those are due to bacteria. Looking at a chemical test and picking out the only thing "wrong" does not necessarily properly finger the culprit.

This is exact my next thought when I can't find out what is the real problem, I will blame bacteria :) Even the number from my ICP somewhat proven high Iodine (in my case) causing problem to my acro, but can't rule out if bacteria or other issue also contributed to the problem.