# red stains in potting mix



## OR.O (Mar 28, 2016)

Hi guys, I've noticed some red stains on marble and dolomite in potting mix. I use RO water and fertilizing with Akerne Rain Mix ( MSU formula ) 110ppm. Could this iron's oxide be toxic for plants? if it was too much...


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## gonewild (Mar 28, 2016)

OR.O said:


> Could this iron's oxide be toxic for plants?



No



> if it was too much...



Yes

What small amount you see is nothing to worry about.

To be "too much' it would have to be bad or toxic otherwise it would not be "too much" :wink:


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## NYEric (Mar 28, 2016)

Stains from the bark.


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## Ozpaph (Mar 29, 2016)

Ignore it. ? tannins from the bark?


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## OR.O (Mar 29, 2016)

Thank you all for your answers,
I ignored about the stains. 

Now I would to use the humic acid, which should increase the absorption of elements (as I read somewhere). 
If the stains were made of ferric oxide, do you think the subministration of humid acid would make too excessive the oxide absorption?


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