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Re: Questions about iron

Aaron <aivers at betamachinery_com> wrote:
> Subject: Questions about iron
> 1.  I understand that some chelated iron can be in the form of Fe++ or Fe+3.
> Can you tell the difference by its colour after being mixed in water?

No, unless you know what you had to start with. Ferric chloride is 
brownish-yellow, ferric oxide is red, ferrous ammonium sulfate is 
lime green, ferrous sulfate is green-blue, and probably every color 
in between.
> 2.  If my chelated iron is Fe+3, is it useful?  Correct me if I'm wrong but
> I thought Fe+3 will only become biologically available only when reduced to
> Fe++ by the plant roots.

True. There's reduction taking place throughout the tank, even 
around and on the fern leaves. The chelated part holds the iron in a 
ligand so it's not as easily converted to rust. Sometimes it depends 
what kind of Fe+3 we're talking about ;-). Ferric chloride (FeCl3) is 
made from ferrous chloride that has been reacted with Cl gas. It 
registers as Fe2+ when tested. 

> 3.  If I mix EDTA chelated iron into PMDD with my moderately hard tap water
> (pH ~8.0), will the EDTA breakdown quickly?  Will the colour change, will I
> see rust in the bottom of the jar?

It should be fine. EDTA breaks down in the presence of light, so 
store in a dark place or brown bottle. Hard water won't hurt. 
Actually the Ca and Mg will chelate once in solution. Yes, the color 
will change, but only if it's colored to start with.

> 4.  I assume the commonly recommend iron level of 0.1 ppm is for Fe++.  If
> my Seachem iron kit measures Fe+3 and my trace mix is Fe+3 what should my
> target level be?

I don't have a Seachem test kit, but if it measures Fe+3, then it 
must chemically convert the ferrous to ferric before reading? 
Sounds plausible.

> 5.  My Seachem iron kit will not register any colour for at least four hours
> and then gets darker the longer I leave it.  Evaporation becomes a problem.
> The next morning it looks as though I have way too much iron, but only a
> little amount of water is left in the cup.  What can I assume my iron level
> to be?

Dr. Morin? Care to shine any light...? 

> Maybe I should just switch to TMG and go out and buy a Hach iron kit...

You could. But, science is supposed to be complicated. Enjoy it! 
I'd wait to see what the others, or Greg, have to say about the test 
kit. Those things aren't cheap. 

Jamie    <"\\\>< Aquatic plants, water chemistry, and cichlids
Greenwood, SC     http://www.ais-gwd.com/~jjirons