Dosing iron

Lazaro777

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Aug 31, 2021
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Hi all, curious of going macro algae one of these days and I came across this thread where Tom Barr is going back and forth with another Phd about the how different chelators (gluconate, edta, dtpa, eddha) affects how macro algae intakes iron:


As much Phdensity that thread had, I must say Mr. Barr is quite an eloquent writer. As a layman who only took one college semester of chemistry, I was able to follow a bit. My understanding is that something like Aquarium Co-op's Easy Iron would do in a macro algae aquarium.

I like how at that level, both parties seem to be inferring a possibility based upon peer reviewed research brought up in that thread. For the time being I have access to a couple of these scholar databases and can "try" to geek out on the articles mentioned.

Fast forward 12 years later, there is a product out that does dose iron that uses a different compound altogether, i.e. Sodium feredetate:


To edit this novel short, which iron source would be ideal? Edta, dtpa, eddha, gluconate or Sodium Feredetate.

Would like to go with one kind and not mix and if convenient to get in powder form, that would be a bonus. As per Dr. Randy Holmes-Farley advice:

 

Allwissend

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I have no experience in marine tanks but I don't see why Easy Iron wouldn't do the job.

There is little to debate about the higher stability of chelated iron compounds especially at higher pH values common in marine tanks. You also have there some articles showing uptake of chelated iron forms by macroalgae. I think if there is a debate it would be in ease of use by specific algae, but that does not seem to be much of a problem so why not add a source of iron that stays available for the algae/plants for longer and does not easily end up at the bottom of the tank or in the filter as precipitate. Seachem has had this gluconate good, EDTA bad rhetoric for a long time but experience shows otherwise, at least in the freshwater planted tanks.

I would not recommend iron gluconate as pills for human consumption because they often contain a lot of other stuff (both numbers and amount) besides the active ingredient. Often it's just filler to make the pill large enough to grab.

Sodium feredetate is just another name for Fe-EDTA with the sodium leftovers from the chelation process.
 
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Lazaro777

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Thanks Allwisend, appreciate how this forum can help out this curious non chemist.

Was wondering if this product could work for diy in a marine tank considering that they have higher pH and alk levels:


This products has hedta. Curious what the h stands for and if would it affect marine tanks at all.

Not in my cards yet to get master's in chemistry too so appreciate the short chem lessons, that apply to this hobby, anyone has to offer.
 

Allwissend

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HEEDTA or HEDTA is slightly better than EDTA in terms of stability depending on the pH. Some sources recommend it's use as it seems to be less likely to precipitate with phosphates, but can't say I have measured this effect first hand. The extra H comes from hydroxyetyl- but more often it's written as HE (HydroxyEtyl-). It's one oxygen atom short of EDTA actually, but that slightly changes how the molecule looks in 3D and how the Fe is held and protected.

DTPA will be more stable at higher pH values, so will EDDHA. EDDHA stains the water somewhat pink. Small frequent doses can help with less stable components if you aren't able to cheaply source the more stable forms.
 

Lazaro777

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Okay, so I happen to have a canister of the organic iron chelate I linked above with the hedta.

Perhaps just get a dosing pump, since they are common in that side of the hobby, and try dosing a little bit each day. I think there are some liquid color coated iron test kits that can use to measure or just got by how the macro algae looks.

Yet a couple more chem questions if care to indulge:

will mixing iron chelated with distilled water "break" the chelate or will that occur in the aquarium?

Also, this mixture above also has 1% potassium sulfate. I know the potassium will be consumed, but what about the sulfate?
 

Allwissend

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That sounds good. I would test just to check if there still is iron detectable after a week or so with the dosing.
Chelation should not be broken in solution with distilled water kept away from UV light. Many micronutrient mixes are acidified slightly (ph~5) with ascorbic acid (for example ~1 to 6 g/L) to keep the chelation for a long time. 0.4g Potassium sorbate is also added to prevent mold growth. These two steps are optional in my experience if you work with fresh distilled water and use the mix within the month. In the aquarium a part of the Fe-chelate is broken but plants and algae(?) can take up the chelated iron directly.

Plants / Algae also need sulfur ,taken up as sulfate. It is a macronutrient. They use it for various molecules, for example to make amino acids cysteine and methionine. Because it is abundant in tap water or added with Ca, Mg or K it is often omitted from 'macro' fertilizers.
 

Lazaro777

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Okay, so sulfate is a Macro! I guess that's why most products contain something-sulfate, this-sulfate and that-sulfate, or is it because they are cheapest to manufacture.

Btw, just found this, although I think it's talking about terrestrial plants:


Thanks for letting me catch a glimpse into this world.
 

Allwissend

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In part it helps because it's a macronutrient. Most salts with it are rather stable and easy to store and plants and animals have good tolerance for it's accumulation. In the environment it can be removed as H2S gas through natural processes. In small quantities in the open air this is not a problem. And yeah cheap to find / mine. The most common alternative to sulfate salts are chloride salts ( CaCl2, MgCl2, KCl...). While Cl is a micronutrient, many plants don't tolerate high concentrations of chloride ions so it needs more care in the application. For example some aquarists prefer using KCl to K2SO4 as the solubility of KCl is a lot higher.

Plants are awesome like that. Terrestrial plants have a hard life, their uptake is mostly through the roots and often depends on water availability and movement in /out of the plant to bring the nutrients. Our aquarium plants are spoiled, nutrients for grabs at leaf level :D