How important is iron? - Fertilizing - Aquatic Plant Central

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Old 10-31-2004, 03:18 AM   #1 (permalink)
 
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Default How important is iron?

I have never cared much for dosig iron in my tank. I dose everything else very carefully, and I know what happens if i get low on no3 or po4. But I read that several people on other boards keep stressing the importants of dosing iron since it's so important for the photosyntesis. But I have keep my high-tec tank running under with a wide variety of light and plant species over the last two years now without ever dosing more than a standard PMDD dose of traces (one tbls). I dose around 20ml of this a day. When testet, my fe leves are around zero... So, in the name of science I startet dosing iron for a duration of about a month, and much as i expectet nothing changed during this periode.

I keep difficult species like Macranda and Walliichii , but I yet to try my hands on species more demaning than this. That said, both of this grows like crazy like they have always done.

So, is iron really that important? Is there any signs of defficensis beside yellow leaves?
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Old 10-31-2004, 04:33 AM   #2 (permalink)
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Do plants need Fe?
Sure they do, plants can not grow healthy without it. The question is how much they really need. Well, that depends on the specie and on the amount of light. Higher light accelerates the need for more Fe.
You are dosing Fe already with the PMDD mix because it does include TE trace elements. Additional source of Fe may be tap water and substrate.
The amount required is so small no lfs test kit can read.

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Old 10-31-2004, 04:42 AM   #3 (permalink)
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I agree, here in the Nordic countries iron have been all the rave for centuries. Clay and Ferrogan - that has been the prevailing tip for planted tanks despite folks getting initial thread algae blooms from hell.

I very seldom dose micros, compared to KNO3 and KH2PO4, and I almost never see any iron deficiencies in my own tank or other Swedes tanks. I raise my eyebrows when someone have managed to take a pic of the characteristic iron deficient pale/yellow/white new growth.
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Old 10-31-2004, 05:04 AM   #4 (permalink)
 
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Quote:
The amount required is so small no lfs test kit can read.
Recommended value i think is around 1ppm, is this right? I am no where near this, and still evert plant species I have ever tried has done great in my tank.

To get a clue to how important iron seems to be here in norway, is's normaly recommended to dose before dosing no3 or po4. Madness in my eyes, but I can't really be sure from my limited experience.

I have been the proud owner of a tiny bottle of ferrogan for the last ten years, never opened it, never will I think

I would love to get more input on this, but so fare I would say that we all agree that the iron you get from your traces and tap water should be enough even for a high light tank?
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Old 10-31-2004, 06:22 AM   #5 (permalink)
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I think the amount of traces one needs is based on two things. Obviously specific plant requirements (Echinodorus sp. need alot of Fe available while Anubias need much less) is first to consider. Second is, how hard are you pushing your tank? A high light tank maintained with minimum marcos is going to need much less Fe and trace than a tank pushed to the limit with very large weekly amounts of NO3 and PO4. I think the amount of PO4 might, to some degree, have a correlation to the amount of Fe/trace a tank requires.

As example, 4wpg, 30ppm CO2 and fast growing stem plants. The stemscan take up max of about 5ppm NO3 a day. This assumes optimum growing conditions. That would mean this example tank would need very high doses of PO4 to "fuel" the high NO3 uptake. The amounts of PO4 I am not sure but I would guess 3-4ppm a week, if not more. This means two things. First, this example tank will need a lot more Fe and trace to prevent deficiencies due tot he extremely high plant growth. If trace(including the important Fe. Mg, Mn, etc but also the lesser common vandium, boron, zn, etc) nutrients are not allowed to become limiting either, your left with a tank who's growth is limited only by the physical limitations of speed with which the plants can carry out photosynthesis, just as you can only run so fast no matter how good of shape you are in.

Maybe, hopefully, what was in my head made sense when I typed It would be great if someone could fill in the other max's I don't know, ie: max PO4 uptake under optimum conditions, at what point can plants no longer photosynthesize faster, etc.

To make a long story short, you can probably guesstimate at the amount of Fe/trace your tank will need based on your Macro dosing.
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Old 10-31-2004, 08:17 AM   #6 (permalink)
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TE trace elements ratio analysis of dry plant tissue




If it was so necessary to dose 2 ppm of Fe then we would have to dose also the rest of the traces, Mn, Zn, Cu and B in quantities to keep the plant tissue ratio healthy. For 2ppm Fe, there would have to be 0.1 - 0.4ppm Cu dosed daily. That would accumulate to concentrations of 0.7-2.8 ppm of Cu per week. There is something wrong.

Plant-ProdŽ Chelated Micronutrient Mix http://www.plantprod.com/catalogue/0...nutrients.html


Where is the need for extra iron coming from?

Thank you,
Edward
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Old 10-31-2004, 08:49 PM   #7 (permalink)
 
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Bioavailable Fe is not the same as total Fe.
Fe complexes to some 15-20 different forms when added to water.
Organic forms of complexion are even more numerous.
The actual pool of Fe that is plant available is quite low, this maybe true of other trace cations. Eventually some of these complexes are slowly broken down by bacteria.

I believe Paul suggested 0.1ppm for the PMDD original formula.
This also assumes that all the iron is bioavailable.

But this was for a low light, moderately CO2 tank(10-15ppm CO2, 1.5-2w/gal of NO FL's).

Add 2x much of both CO2/light and the growth rate will dramatically increase.

I add everything to excess except NH4.

CO2~30ppm is my target
NO3-10-20ppm lately
PO4-1ppm
K+ 20ppm
GH 5 or more
Traces, 5mls 3x a week/80 liters

Rather than trying to measure something that is problematic(Fe test kits also have many issues/problems),

Add everything else, but Fe/traces, then slowly add more trace mix till you no longer see any improvement in plant health/coloration/growth etc.

Take 2-3 weeks before passing any judgement on the plant's condition with a given routine.

Say add 2 mls 3x a week for 3 weeks, then 4mls 3x a week for 3 weeks, then 6 mls 3x a week and so on.

Once you have hit the high max point, where adding more does not improve plant any more, then that's the amount you will want to add.

My topped out value was 5mls/3x a week in 80 liters at high light, NO3, PO4, K, GH, CO2 at 30ppm.

Adding more did not help beyond this volume/tank size.

Trace volume /frequency/tank volume is a more consistent method than a test kit.

You don't need a test kit doing that method.
Takes time, but gets you to focus on the macro nutrients well first, which is not a bad thing.

Regards,
Tom Barr







NO3,
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Old 10-31-2004, 11:57 PM   #8 (permalink)
 
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Thank you both! The last two posts where of great help. I guess I'll just trow away my ferrogan bottle along with the myth of dosing extra iron. I will however try your tips on micro nutriens Tom to see if I will notice any improvments in growth and healt!
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