# Why to dose extra iron?



## Sacha (15 Mar 2014)

Not sure what to entitle this thread, as my questions are quite broad.

I was reading up about EI dosing online and notice that quite a few people dose extra iron.

Then I got thinking about my own EI mix, and whether I should alter it/ dose less of one thing/ more of another.

How do we know when we need to add extra iron/ magnesium etc? It's straightforward knowing how much phosphate or nitrate to add to a mix, but what about the trace elements? What prompts people to think that they need to dose more iron, for example?


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## ceg4048 (16 Mar 2014)

People add extra Iron under several mistaken impressions:
1. They think that Iron is required by the plant in greater mass or is of more importance than Nitrogen, when in fact it's the other way around.
2. They think adding more Iron will turn their plants red.

On the one hand there is nothing wrong with adding more Iron. It's not toxic at these levels and there may be a genuine shortage in the tank due to poor distribution or excessive lighting. But on the other hand, Iron products costs a lot more than Nitrogen products, for example, and since the plant needs 500X more Nitrogen than Iron buying more Iron is not the best use of your resources. Of course, many people have the means and the cost of nutrient products is not a big deal. But many others have to watch their pennies, so this becomes an important point worth noting.

It's very easy to know. Iron should be used as a proxy for the other elements because the plant uses 100's of time more Fe than the other micronutrients. If you are low on the other micronutrients then there is a good chance you are also low on Iron, unless you are dosing only Iron and the tap water is low in micronutrients.

Iron or Magnesium shortages are characterized by yellowing of the green leaves or paleness/yellowing in non-green leaves. This occurs predominantly in new leaves and not so much in mature leaves. If you are already adding a trace mix and these symptoms appear, then you can just add twice or three times as much. After a few weeks the color of the new leaves will improve.

Again, if you are adding EI levels of the trace mix and are experiencing these symptoms then that is a strong indicator that your flow and distribution methods are suspect. Most likely, poor distribution will show an effect first in NPK because they are more important. If the plants are not showing deficiencies in N, P, or K but are showing these symptoms, then the cause is most likely an under-dosing of the trace mix.

Trace mixes vary in their composition and so it may be that a particular mix is low in Fe, say 5% or less, when normally we'd like it to be around the 13% mark. So people go out an spend more money for extra Iron when all they need to do is to add twice as much of the same trace mix, which will increase the concentration of the Iron.

Cheers,


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## Sacha (16 Mar 2014)

Great, thank you for clearing that up Clive. So pretty much another thing that I don't need to worry about, unless I see yellowing or paleness of leaves.


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## Martin in Holland (1 Jul 2014)

There is also a product (FE) on the market which helps to get your Hydrangeas in your garden to flower (more) blue. Watch out though, this will be very strong and should be diluted quit a bit before using it in your tank, on a good note it is very very cheap.


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## ian_m (1 Jul 2014)

Martin in China said:


> There is also a product (FE) on the market which helps to get your Hydrangeas in your garden to flower (more) blue. Watch out though, this will be very strong and should be diluted quit a bit before using it in your tank, on a good note it is very very cheap.


My dad used to place bits of cast iron drain pipe in the soil around his Hydrangeas to get them to blue. Not always 100% success usually got some blue and some red. Suitable for adding iron to your tank?


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## Martin in Holland (1 Jul 2014)

Normal steel pipes don't really dissolve well in water......


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## Mr. Teapot (1 Jul 2014)

I think (in my amateur opinion) rust wouldn't be particularly useful to the plants as it needs to be chelated Iron (a form that's soluble in water) to be available to them. I reckon it would also stain everything in your tank a nasty brown/orange colour. 

I also have vague memories of my dad doing the same thing but can't remember if it changed the flower colour.


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