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Dosing iron planted tank

Simon Cole

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25 Dec 2018
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Buckingham
Not usually, sometimes, it depends... are you aware of concepts such as fertiliser compatibility, estimative index (EI) dosing, complete fertilisers, macro and micro mixes, and chelates?
Are we helping on a specific planted aquarium, and would you like to share the details?
Certainly happy to discuss a range of ideas anyway :)
 
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erwin123

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4 Mar 2021
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Singapore
Thanks to UKAPS and the IFC calculator which lists the amount of ferts in common commercial bottles (APT, Tropica , Specialised), it helps me figure out what much Fe and other nutrients I'm adding. If the manufacturer's bottles are used as recommended, there should be enough Iron in commercial ferts and supplementation should normally not be required. If you are dosing EI, then the EI recipe which calls for 0.5ppm Fe is generally considered more than enough.

However, if the issue is very hard water / high pH or other water issues that reduce the availability of Fe to the plants - then the question should not be how much/how often but what form of Fe to dose. Like Simon mentioned, more details will help.
 

_Maq_

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Do you guys dose iron daily? Thanks
Out of layman's enthusiasm for chemistry, I've prepared a potassium-iron-citrate complex. It works fine for me for years. I dose it irregularly, approx. once a month.
People insist on using strongly chelated iron but precipitated iron is not lost to the plants unless it ends up in the filter. Iron in the substrate is subject to rather rapid transformations through both biotic and abiotic processes, and plants are fully able to get what they need through their roots. There's no EDTA in the nature, after all. Many natural chelators exist in the nature, and they are present in our tanks as well.
That said, some species are unable to get iron (and other transition metals) in an alkaline environment full of bicarbonates. If this is the case, overdosing iron & other metals would hardly save them, but it can reach the levels where toxicity is the problem.
 

erwin123

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991
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Out of layman's enthusiasm for chemistry, I've prepared a potassium-iron-citrate complex. It works fine for me for years. I dose it irregularly, approx. once a month.
if you dose it irregularly, does it mean that its not actually needed?

if you go for 1 month without dosing iron (you haven't mentioned whether you do water changes) and there are no signs of iron deficiency in the plant, could it mean that your substrate is rich in iron, or your water source contains some iron?
 

_Maq_

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23 Jun 2022
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Czech Republic
if you go for 1 month without dosing iron (you haven't mentioned whether you do water changes) and there are no signs of iron deficiency in the plant, could it mean that your substrate is rich in iron, or your water source contains some iron?
No. I rather believe it's partly because I have no filter.
You know, normally - without filtration - most of iron precipitates in the substrate. But such an iron is not lost. Living bacteria as well as dead organic matter make iron perpetually transforming, and plants can get it through their roots. Also, humic substances and various other organic compounds function as natural chelating agents of iron & other transition metals.
The only iron which gets truly lost is that which gets trapped in the filter. There, iron oxides adsorb phosphates and other metals. As long as the filter remains well-oxygenated, these compounds are unlikely to dissolve. On the contrary, they accumulate. Haven't you ever noticed that brown powder and brown colored sponges in your filter?
I'm using solely RO+DI water which I mineralize. The content of iron and other metals is below detection. Yet I admit that I don't inject CO2 and dose all fertilizers quite modestly, so my plants grow rather slowly. Therefore, the need of micronutrients is relatively limited, too.
Still, I believe that most people hugely overdose micronutrients. I happened to study a bit an official analysis of tap water in Czech Republic, and I've learned that in most cases no micronutrient fertilizers are needed, with the exception of iron - due to its peculiar behavior.
 
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