Elevated Iron and Manganese in my Fresh-mixed Sea Water... But How?

[dangles]

So I recently had a couple of unexpected (and rapid) fish deaths in quarantine. I ruled out the obvious initial causes (unhealthy fish, ammonia, temp/salinity/etc) and decided to send off an ICP test of my newly-mixed seawater to see if I could find a clue there.

The analysis came back *pretty much* clean except my iron and manganese were elevated (12 mcg/L and 51 mcg/L respectively) - both well above the expected levels. I don't think that explains the fish deaths, but that leaves me wondering... how did those levels get that high?

I'm on well water (a new system) and had a water analysis done prior to building the mixing station. Iron was undetectable, and manganese was 5 mcg/L. The water passes through a softener and then through my 7-stage RODI before filling the mixing bin where I add Tropic Marin Pro Reef salt.

I have not had any issues in my display thankfully, but how did those numbers get that high? Triton suggested the obvious culprits (overdosing trace - which I don't do, especially in my mixing bin), rusting metal components (there are none in my mixing bin), or some other contamination (which isn't helpful).

I'm leaning toward either a bad test (the ICP or the well water test I did), bad batch of salt (unlikely) or somehow my RODI system is malfunctioning.

Which stage would be responsible for filtering those elements out? Maybe one or more of my RODI stages needs replaced?

What else should I consider? And at what level is iron/manganese harmful?

Thanks!

 

[argonaut]

This is due to trickling agents. They break down quickly. You should therefore wait a few days with the icp and not send in freshly prepared water straight away.

 

[dangles]

This is due to trickling agents. They break down quickly. You should therefore wait a few days with the icp and not send in freshly prepared water straight away.

Trickling agents? Can you explain? My samples took approximately 5 days to arrive at the Triton testing facility. Does that make a difference?

 

[argonaut]

In addition to iron, manganese is also often used as an anti-caking agent in salt production. However, both elements are very sensitive to precipitation, i.e. after a few days there will no longer be much of them dissolved in your tank, especially if you have a high PO4 value.

Anti-caking agents (also known as anti-caking agents or anti-agglomeration agents) are separating agents that are added to crystalline substances such as sea salt to prevent the individual crystals from clumping together, primarily for the purpose of making them easier to use in machines. For example, sodium hexacyanidoferrate(II) (Na4[Fe(CN)6])

That is quite normal and every sea salt i know has elevated levels at the beginning.

 

[dangles]

In addition to iron, manganese is also often used as an anti-caking agent in salt production. However, both elements are very sensitive to precipitation, i.e. after a few days there will no longer be much of them dissolved in your tank, especially if you have a high PO4 value.

Anti-caking agents (also known as anti-caking agents or anti-agglomeration agents) are separating agents that are added to crystalline substances such as sea salt to prevent the individual crystals from clumping together, primarily for the purpose of making them easier to use in machines. For example, sodium hexacyanidoferrate(II) (Na4[Fe(CN)6])

That is quite normal and every sea salt i know has elevated levels at the beginning.

That makes a lot of sense! Thank you!

 

[Randy Holmes-Farley]

I would not assume those are anticaking agents, but regardless, I see no reason to be concerned. Some folks dose iron to levels far higher, and manganese is rapidly depleted.

 

[argonaut]

Here in Germany there is a well-known manufacturer of sea salt, Fauna Marin. They carry out an ICP analysis for every batch, e.g. here: https://www.faunamarin.de/wp-content/uploads/2024/01/Professional-Sea-Salt-23525.pdf
In case of manganese and iron they note: "Anti-caking agents have no bioactive effect and are removed by skimmers"

I am neither a manufacturer nor a chemist. I don't know whether these are really anti-caking agents or perhaps unavoidable impurities. However, it can be said that with any sea salt, regardless of the manufacturer, these rashes always occur at the beginning and that, as you have already said, it is not a problem.

 

[dangles]

Further confirmation for the “anti-caking agent” theory…

I had sent an email to TM and Hans-Werner Balling replied, also suggesting that as the likely explanation.

Thanks for all the input everybody.

 

[Randy Holmes-Farley]

I do not know if it is actually used in salt mixes, but the sodium hexacyanidoferrate(II) (Na4[Fe(CN)6]) will not be skimmed out.

 

[Marc Pardon]

So I recently had a couple of unexpected (and rapid) fish deaths in quarantine. I ruled out the obvious initial causes (unhealthy fish, ammonia, temp/salinity/etc) and decided to send off an ICP test of my newly-mixed seawater to see if I could find a clue there.

The analysis came back *pretty much* clean except my iron and manganese were elevated (12 mcg/L and 51 mcg/L respectively) - both well above the expected levels. I don't think that explains the fish deaths, but that leaves me wondering... how did those levels get that high?

I'm on well water (a new system) and had a water analysis done prior to building the mixing station. Iron was undetectable, and manganese was 5 mcg/L. The water passes through a softener and then through my 7-stage RODI before filling the mixing bin where I add Tropic Marin Pro Reef salt.

I have not had any issues in my display thankfully, but how did those numbers get that high? Triton suggested the obvious culprits (overdosing trace - which I don't do, especially in my mixing bin), rusting metal components (there are none in my mixing bin), or some other contamination (which isn't helpful).

I'm leaning toward either a bad test (the ICP or the well water test I did), bad batch of salt (unlikely) or somehow my RODI system is malfunctioning.

Which stage would be responsible for filtering those elements out? Maybe one or more of my RODI stages needs replaced?

What else should I consider? And at what level is iron/manganese harmful?

Thanks!

Is it possible to share your icp results for the newly mixed batch with tropic Marin pro reef salt? Because TM doesn't have this function and I want to know what this salt does with the macro and micro elements ......

 

[dangles]

Is it possible to share your icp results for the newly mixed batch with tropic Marin pro reef salt? Because TM doesn't have this function and I want to know what this salt does with the macro and micro elements ......

https://www.triton-lab.de/en/showroom/icp-oes/117542

The elevated manganese is normal. That's an anti-caking additive that levels out soon after it's mixed.

 

[Randy Holmes-Farley]

https://www.triton-lab.de/en/showroom/icp-oes/117542

The elevated manganese is normal. That's an anti-caking additive that levels out soon after it's mixed.

Why do you think salt mixes use manganese as an anti caking agent?

 

[rtparty]

Is it possible to share your icp results for the newly mixed batch with tropic Marin pro reef salt? Because TM doesn't have this function and I want to know what this salt does with the macro and micro elements ......

I did a full blown test on more than a dozen salts. It’s in my signature.

I haven’t looked at the results in quite some time but I don’t recall any salt severely lacking anywhere in the trace department. The only salt I really saw as a “failure” was Brightwell. I went through the whole bag trying all sorts of ways to mix it and it always left weird stuff in the container and parameters were always off from advertised. Could have been a bad batch. I certainly wasn’t going to buy more and give it a shot when there are already a bunch of great salts to choose from

 

[Christoph]

Hi!

The manganese anti caking is one of the "reefing urban legends" that is difficult to get rid of:

To the best of my knowledge (and im happy to change my opinion here) there is no manganese based anti caking agent, and the elevated manganese that is often found in salts is an impurity.

The manganese itself is not problematic imo, but when you analyze the brown "smear" that sometimes builds in salt mixing stations, you find (besides precipitated iron and manganese) very significant levels of various essential trace elements. In my opinion the precipitation of manganese (and iron) co-precipitates other elements, thus lowering trace element availability in salts. For this reason i recommend picking salts with reasonable Fe and Mn levels.

Iron however is used as anticakig agent (ferrocyanide). The fate of the ferrocyanide is not very clear to me. Direct skimming is unlikely as Randy already stated - so i would suspect biological breakdown, even though ferrocyanide is a fairly stable complex compound.

All the best,
Christoph

 

[Marc Pardon]

https://www.triton-lab.de/en/showroom/icp-oes/117542

The elevated manganese is normal. That's an anti-caking additive that levels out soon after it's mixed.

Thanx!

 

[Randy Holmes-Farley]

Thanks, Christoph.

 

[dangles]

Why do you think salt mixes use manganese as an anti caking agent?

Here. Maybe I misunderstood?

 

[Randy Holmes-Farley]

Here. Maybe I misunderstood?

Ok, yes, that perhaps means iron.

 

[Pod_01]

Ok, yes, that perhaps means iron.

Randy when I read the reply it sounded like the anti caking agent contains both. Both are metals…

I just don’t know if that is reasonable interpretation or assumption…

 

[Randy Holmes-Farley]

Randy when I read the reply it sounded like the anti caking agent contains both. Both are metals…

I just don’t know if that is reasonable interpretation or assumption…

Most trace elements are metals. I don’t know what exactly he meant.