I've been doing a lot of reading on chelated vs non chelated iron. I found a long thread on The Krib. Dr. Greg Morin from Seachem got engaged in a lengthly discussion on the chelated vs non chelated iron issue. I don't even pretend to know anything about chemistry, but the thread was interesting and I picked up a few things.

If I understood Morin correctly Seachem uses ferrous iron in flourish and its iron supplement product. Although it is not stable, ferrous iron is taken up more easily by plants and ultimately they will take in more iron since plants have to expend more energy to access iron in the chelated form which stays in solution longer.

I also get the sense that there are a number of different chelators which seem to relate to the strength of the bond among other things.

What form of iron is the best to use ? What water parameters are relevant to the choice ? Are certain forms of iron more likely to bond with phosphate or more problematic in hard water ? If one does an iron test, does the test measure only iiron that is in a state that is not available to plants ?

I don't know why I think about these things, but I do.


Henry

Plants possess 0.06% Fe by dry weight.
The energy difference is hardly significant in the total energy budget for a plant.

Plants almost exclusively are adapted to Fe3+ uptake as Fe2+ is chelated to Fe3+ once inside the plant cell for transport anyway............

So...........

You may read the Fe/Mn article here if you are interested in the BarrReport articles.
It goes over uptake mechanisms and what is known.

Unchelated Fe will not exists in the free form in our water, we need to have it bound by a chelator to have it be taken up by the plant leaves.

Note, in the sediment, reduction via the roots and bacteria(under the right conditions) will provide the usable form of Fe by that uptake method.

But never in the water column.


Regards,
Tom Barr

Tom are you saying that ferrous Iron or Seachem's Iron supplement is worthless to the planted tank community? I've been using Seachem's Iron for quite some time and never questioned its effectiveness. If it is useless in this application I would like to know so that I can switch to a chelated Fe supplement at once. Thanks.

Never said nor implied Fe2+ vs Fe3+ was useless.

Plants will take in either form and then they have their own endogenous chelator which uses a Fe3+ cation, not as Fe2+ which is rare in general and with that extra electron, pretty nasty inside unless you have tight regulation, which the plant does.

I just do not buy the reasoning that it's better than any other chelator based on energy requirements at the whole plant level and no one has ever shown that, it's speculation, not plant physiology, on Greg's part.

I've used more than just Seachem and several other chelators for traces over many years, I'd like to see if anyone could prove a difference.
I could not at least in terms of growth rates/dry weight biomass etc.

I do not think Greg nor any aquarist has/will any time soon either.


Regards,
Tom Barr

So, if we place the rusty nails into the substrate where the oxygen content is low, and the plants will get their nutrients through their roots (like iron) that are bound to organic substances. But how much time will it take for a rusty nail to turn into an availble nutrient to the plants?

I used iron filings myself.

I think it's hard to determine unless you have a Redox probe and/or a DO probe.
Then you can measure the amount of reduction that is optimal for Fe reduction.

About 200mv range or so.

But...........what about when the Fe is in aerobic water column? Then it gets oxidized back to rust again.

So the leaves never get it unless................they transport a generally non mobilie nutrient all the way from the roots to the apical tip. Or you use a liquid source like DTPH, gluconate, Glycine, ETDA etc.

I use the shelf life in the water column based on KH for each chelator type rather than an energetics model. I think simply having the Fe in any form is best, but you can also address the energetics by comparign a weak and strong chelators, that would provide low energy, while the strong chelator would provide longer exposure time/frequency.

The best benefits of each theory.
That's what the Barr's Matrix will have that Greg sells, at Aquarium Plant Food - hobbyist taking care of hobbyist … | Greg Watson's Planted Aquarium Fertilizer

Hopefully this June.

Regards,
Tom Barr

I can't prove it, but I feel that gluconate chelators aren't so effective in water with higher KH levels. I was using Seachem's Flourish and Flourish Iron in a tank with a KH of 15 for a while and then gave TMG a try. I did notice quite a difference.

There was much less of a difference between Flourish and TMG in water with a KH of 5, though subjectively I still prefer TMG.

A long time ago, I thought your argument was a good one ... so I bought a dry Iron Sulfate with the thought that it might make a good substrate additive when setting up a new aquarium.

So I did several tests. I poured a thin layer into the bottom of a new 55 gallon tank and then covered that with ordinary "red" colored aquarium gravel. In a second tank, I poured the same thin layer and covered it with a similar layer of red gravel and then a layer of sand. And in the third tank, I simple used the red aquarium gravel. I then dosed all three tanks using the EI method.

I was expecting some improvement in at least one of the tanks using the Iron Sulfate in the substrate.

I was concerned that the Iron Sulfate would leach out of the tank that was just covered by gravel.

I could detect no visible difference in the health of the plants between the tank with Iron Sulfate and Red Gravel and the tank that simply had the red gravel.

I could detect no visible difference in the growth rate of the tank with the sand covering the iron sulfate and the red gravel, however, the tank was susceptible to a black slime type bacterial algae that was difficult to keep in check - that I have never had in any of my other tanks.

That is not a perfectly controlled experiment ... and it is only an experiment with relatively hard water with GH/KH around 11 ... but it gave me enough information to decide that I did not think it was necessary or appropriate to sell ordinary Iron Sulfate ...

Greg Watson
The "other Greg" in the context of this thread <grin> ...

I've seen this as well. Many noted this years ago.That would be the best test to show some differences between them.

But at soft water conditions, have you or anyone seen any differences?
I haven't.

So I questioned whether there is any real advantage to Seachem's arguments.
I have not seen such observations myself.

Regards,
Tom Barr

When using TMG is there any need to supplement Fe in addition to it, or does TMG have all desirable micros in proper quantity? Thanks..