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Hello all. Ive been spending the night looking through old posts about chelated iron but havnt really seen any brands that someone recommends. if there is a brand that you all use that i can order online can someone please let me know what it is and maybe a website. im getting that yellow leaf right now and would like to correct it. thanks for any help and have a nice day.

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Interesting.  I didn't read carefully enough.  I have EDTA.  However, I've used it with basil before and it cured the iron deficiency in days at approx. 6.8-7.0 pH.

Per Alex's question, my bottle says 1 tbsp per gallon.  However, I'd add it slowly.  Adding a whole 16 oz bottle to 450 gallons killed ten trout last month.  I think it takes up oxygen or something, because adding three bottles last summer barely affected tilapia at all.

EDTA breaks down into glyoxylate and formaldehyde. The trout have a ld50 of 118ppm for formaldehyde - so that's probably what killed them.  

Interesting.  I didn't realize that.  I'll be more careful now.  

Does it break down further from that into something else, from those two byproducts?  The reason I ask is that the rest of my trout survived and were perfectly fine a few days later and are still doing fine.  

The ones that died looked like their gills had been engorged.  One was bleeding from the gills.  That's what made me think it had to do with oxygen, though I suppose those products could harm their gills as well.  

EDTA has also been proven to be toxic to plants as well...the jury is still out on DTPA plant toxicity (but it appears fine in even remotely sane quantities). 

I've learned to live with the slight red tint that Fe-EDDHA causes in my water. Fe-EDDHA is a bit pricier and all...but well worth it (to me at least).

You would never ever need more than 2-3ppm of Fe in your system regardless of what you were growing.

Vlad - I am aware of one university study that found DTPA was inhibiting germination of one specific species.....  going off memory here.....

Right...probably a fungal species...at particularly low pH levels...much, much lower than we'd ever encounter in an aquaponic set and setting (pH 3-5). DTPA Toxicity issues have been brought up in academic/research circles...Not much of any relevance that I can discern. Most of it revolves around inhibiting uptake of things like Cu at rather ridiculous levels of DTPA present...or other non-aquaponic-relevant issues, like sequestering (through ion-exchange) heavy metals such as, cobalt, einsteinium, lanthanum, nickel, promethium, scandium, strontium, ytterbium  blablablaaaa...those things then being up-taken by plants. So it seems that DTPA itself  doesn't appear to be plant toxic...but if you are growing in a field downwind from a nuclear (fallout) plant ity may aid in sequestering some un-wanted heavy metals that would them be taken up by your plants. So it seems like in certain scenarios it would facilitate toxicities, rather than being toxic in and of itself...

I just like the effective range that Fe-EDDHA offers, especially for 'research' purposes...like for instance, a few years back I grew out some 2,000+ sell-able plants in an environment where the pH was above 8...just to disprove some common myths (to myself if nothing else...for 'shits and giggles' as they say...). That would not have been possible with Fe-DTPA. In reality, the only plant essential elements that experience "lock-out" at that pH level are Fe, P, and B (the latter which is important in cell differentiation...this plays out mostly in terms of pollen production...but the plants I did this with were greens and lettuces, so i wasn't interested in bringing them to flower/seed anyhow). I've never been able to induce a Mn deficiency without the use of de-mineralized water in a non-AP setting regardless of how high the pH was...so I'm only counting Fe, P and B as potential elements subject o pH related lock-out.

Howdy Mr. Jovanovic. from a first time poster here and long time reader of your posts, love'm!

You stated that, "would never need more than 2-3ppm of Fe in the system"... I am curious how you determine this...

It appears all iron tests are not created equal and only some iron tests will test for EDDHA and some will only test for DTPA and some will only test for non-chelated iron. Also, from the research I have done, it appears that most common aquarium iron test kits only test for chelated EDTA and non-chelated iron such as ferrous sulfate.

Can you provide a hyperlink reference to a test kit that can test for Fe(DTPA) and / or Fe(EDDHA) ??

Hope you can provide some clarity here. Thanks for sharing your time. :)


Vlad Jovanovic said:

EDTA has also been proven to be toxic to plants as well...the jury is still out on DTPA plant toxicity (but it appears fine in even remotely sane quantities). 

I've learned to live with the slight red tint that Fe-EDDHA causes in my water. Fe-EDDHA is a bit pricier and all...but well worth it (to me at least).

You would never ever need more than 2-3ppm of Fe in your system regardless of what you were growing.

Not a fungal species. I'm trying to find the web page - it was from a university class studying germination of a flower, and the professor's lab notes made mention of changing the standard nutrient recipe from Fe-DTPA to Fe-EDDHA because they found Fe-DTPA was inhibiting germination of that specific species. 

I use and recommend Fe-EDDHA because Fe-DTPA breaks down too quickly when exposed to sunlight. Since my Aquaponics system is outside in the sunlight....

I also aim for 2.5ppm of Fe.

Vlad Jovanovic said:

Right...probably a fungal species...at particularly low pH levels...much, much lower than we'd ever encounter in an aquaponic set and setting (pH 3-5). DTPA Toxicity issues have been brought up in academic/research circles...Not much of any relevance that I can discern. 

Interesting, so Fe-DTPA was actually inhibiting the germination of a plant species? Wow. That is not very cool at all.

Scott Roberts said:

Not a fungal species. I'm trying to find the web page - it was from a university class studying germination of a flower, and the professor's lab notes made mention of changing the standard nutrient recipe from Fe-DTPA to Fe-EDDHA because they found Fe-DTPA was inhibiting germination of that specific species. 

I use and recommend Fe-EDDHA because Fe-DTPA breaks down too quickly when exposed to sunlight. Since my Aquaponics system is outside in the sunlight....

I also aim for 2.5ppm of Fe.

Vlad Jovanovic said:

Right...probably a fungal species...at particularly low pH levels...much, much lower than we'd ever encounter in an aquaponic set and setting (pH 3-5). DTPA Toxicity issues have been brought up in academic/research circles...Not much of any relevance that I can discern. 

Howdy 

The 2-3ppm number comes from standard hydroponic research. Much of that research inevitably has it's roots in the 1950's work of Dr.'s Aron and Hoagland - The Water Culture Method for Growing Plants Without Soil, Circular 347, California Agricultural Experiment Station, University of California, Berkeley, CA. 

I believe in Hoagland's "Solution No1" he used iron ammonium citrate, while in "Solution No.2" an iron chelate was used (to the tune of 2ppm). Personally I think that even this number is excessive (especially for lettuce and greens), but I suppose folks are in luck in terms of irons unique trait of not behaving antagonistically towards any of the other cations (within reason), that and the fact that plants can engage in "luxury consumption" of iron without any apparent deleterious effects. So excessive iron dosing (again, within reason) probably only impacts the pocket book negatively...and not so much the plants. But we should still calculate out an amount...as opposed to "just tossing some in there and seeing if the plants green-up"

mg/L = Solute (mg)                                                     

             Solvent (L)

I shoot for 1-1.5 ppm or because I'm a cheapskate. I only can really know with any certainty how much iron is in any given system the very first time that I add it. After that we top up our water, plants uptake some iron etc...and I can no longer say for certain how much iron is actually present. I do however like to have some iron sensitive plants in a system that will start to exhibit signs of iron deficiency (inter-venal chlorosis in the youngest leaves) before my cash crop does. This lets me know it's probably time to add iron soon.

I could not with any confidence refer you to a test kit or brand, since I've not used them. I'm not even sure that a titration type test kit even exists which could reliably detect levels of Fe-DTPA or Fe-EDDHA...Hence the initial calculating/measuring, observing plants, then (hopefully somewhat intelligent) 'guesstimation'...of additional iron dosing.



Charles Sublette said:

Howdy Mr. Jovanovic. from a first time poster here and long time reader of your posts, love'm!

You stated that, "would never need more than 2-3ppm of Fe in the system"... I am curious how you determine this...

It appears all iron tests are not created equal and only some iron tests will test for EDDHA and some will only test for DTPA and some will only test for non-chelated iron. Also, from the research I have done, it appears that most common aquarium iron test kits only test for chelated EDTA and non-chelated iron such as ferrous sulfate.

Can you provide a hyperlink reference to a test kit that can test for Fe(DTPA) and / or Fe(EDDHA) ??

Hope you can provide some clarity here. Thanks for sharing your time. :)


Vlad Jovanovic said:

EDTA has also been proven to be toxic to plants as well...the jury is still out on DTPA plant toxicity (but it appears fine in even remotely sane quantities). 

I've learned to live with the slight red tint that Fe-EDDHA causes in my water. Fe-EDDHA is a bit pricier and all...but well worth it (to me at least).

You would never ever need more than 2-3ppm of Fe in your system regardless of what you were growing.

Aha - I found my reference. DTPA inhibited germination of Arabidopsis seeds. URL http://www.ag.unr.edu/cramer/Arabidopsis%20Hydroponics.doc

Btw - I used the Hannah checker iron meter - and it detects my FeDTPA and FeEDDHA perfectly.

What was there reasoning behind DTPA inhibiting germination? I must say i am eager to test this at home to find out for myself. nm just saw vlads post

Scott Roberts said:

Not a fungal species. I'm trying to find the web page - it was from a university class studying germination of a flower, and the professor's lab notes made mention of changing the standard nutrient recipe from Fe-DTPA to Fe-EDDHA because they found Fe-DTPA was inhibiting germination of that specific species. 

I use and recommend Fe-EDDHA because Fe-DTPA breaks down too quickly when exposed to sunlight. Since my Aquaponics system is outside in the sunlight....

I also aim for 2.5ppm of Fe.

Vlad Jovanovic said:

Right...probably a fungal species...at particularly low pH levels...much, much lower than we'd ever encounter in an aquaponic set and setting (pH 3-5). DTPA Toxicity issues have been brought up in academic/research circles...Not much of any relevance that I can discern. 

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