Discoloured macro mix . . .

Wookii

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I am auto-dosing EI ferts, and so a little over a month ago made up 1.5 litres of micro and macro mixes in separate containers using APFUK salts from their ‘starter kit’.

However the macro mix has changed from being completely clear to become very discoloured and has some ‘bits’ in the bottom of the container that could be some sort of precipitation:

upload_2020-2-23_16-46-50.jpeg


upload_2020-2-23_16-47-1.jpeg


I have another bottle of macro mix that I made up a month before this one, and that is still completely clear.

The only difference between them was the older mix used boiled and cooled tap water, and the newer discoloured mix used boiled and cooled DI water, plus has added ascorbic acid.

Should I be concerned about this macro mix, and it possibly affecting the availability of the nutrients it contains? If so I can remix some - though should I omit the ascorbic acid this time if that has caused the discolouration?
 

SRP3006

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I use the same ferts from apfuk and its strange that your macro is the same colour as my micros mix. My macro always has been completely clear whereas the micros are a tinted colour.
Im not sure but I'd probably pour it away and make another batch.
 

Sammy Islam

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I use the APF salts too and my macros are always clear, my micros are more that colour though.

Weirdly i do get a bit of white powder at the bottom of my macros bottle so i guess maybe the k is coming out of solution. Seeing as you have something at the bottom i would think something is coming out of solution but no idea why its brown/orange
 

Wookii

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Thanks guys, the only thing I can think then is it must be the Ascorbic acid. Are either of you adding that to your macros?
 

SRP3006

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No I don't add anything but the salts. Make up 1l at a time in RO, used to use cooled boiled water though. Never changed colour or had any precipitation that I've seen, but I always mix up in a separate mixing bottle and leave for a few days.
 

Hufsa

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I have separate solutions for N, P and K and only my P solution has color. All of them have potassium sorbate and ascorbic acid in them. I dont know if this helps.
 

papa_c

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I had the same issue when using potassium Sorbate and ascorbic acid.....stopped using it and don't have the problem any more. Never got to the bottom of the reason.
 

Jayefc1

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The potassium Sorbate and ascorbic acid.are mainly used for a all in one solution to stabilise the water ph to stop mould and keep the ph to 6 hence stopping the fe coming out of the mix not seen them.used in micro and macro individually I make all in one with boiled tap water on a 500ml bottle and have no issues
 

Oldguy

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become very discoloured

Looks like iron is coming out of solution. Best to keep stock bottles of ferts in separate bottles & only mix together small amounts for auto dosing. Definitely keep iron/traces separate from your macros. Mix your iron/traces with RO or rain water and not tap water, which is fine for your macros. Calcium and magnesium salts in tap water will displace iron and other chelated transition metals from their chelates and they will become simple non complexed ions in solution and be readily oxidized to 'rust' and become a deposit on the bottom of the stock bottle. Chelates can also be susceptible to photo degradation, so dark bottles or dark cupboard for storing stock solutions.

Hope this helps.
 

Wookii

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Looks like iron is coming out of solution. Best to keep stock bottles of ferts in separate bottles & only mix together small amounts for auto dosing. Definitely keep iron/traces separate from your macros. Mix your iron/traces with RO or rain water and not tap water, which is fine for your macros. Calcium and magnesium salts in tap water will displace iron and other chelated transition metals from their chelates and they will become simple non complexed ions in solution and be readily oxidized to 'rust' and become a deposit on the bottom of the stock bottle. Chelates can also be susceptible to photo degradation, so dark bottles or dark cupboard for storing stock solutions.

Hope this helps.

The discoloured bottle is macro only, there’s no iron in it.
 

Oldguy

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discoloured bottle is macro only

I am not familiar with branded ferts. My macros are pot nitrate & pot dihydrogen phosphate, both lab grade. I also use pot sulphate & magnesium sulphate both garden fert grade (about £2.30 a kg). The pot sulphate throws a small milky ppt which I decant. Each is in their own bottle. As are my EDTA Iron & Trace mix.

Your solution in the picture still looks like an iron salt in solution. Are there any iron salts in your general fert salts, perhaps as an impurity.

Sorry I cannot help further.
 

Wookii

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I am not familiar with branded ferts. My macros are pot nitrate & pot dihydrogen phosphate, both lab grade. I also use pot sulphate & magnesium sulphate both garden fert grade (about £2.30 a kg). The pot sulphate throws a small milky ppt which I decant. Each is in their own bottle. As are my EDTA Iron & Trace mix.

Your solution in the picture still looks like an iron salt in solution. Are there any iron salts in your general fert salts, perhaps as an impurity.

Sorry I cannot help further.

I don’t think so, the ferts are from Aquarium Plant Foods UK, so they’re not branded as such, and they should be just pure raw salts.

As I say I have mixed the salts in another bottle previously, and that remained clear. The only difference was the clear one used boiled tap water, and the discoloured one used DI water, plus the discoloured one had Ascorbic acid added.

If I remix, as I said above, I won’t add the Ascorbic acid to see if that is what has caused the discolouration.
 

papa_c

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I won’t add the Ascorbic acid

From my experience it is this that causes the brown tint. Immediately I stopped adding it my macros they remained clear I mix up enough for 2 months at a time. Nothing else has changed and I'm still using RO water.
 

Wookii

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From my experience it is this that causes the brown tint. Immediately I stopped adding it my macros they remained clear I mix up enough for 2 months at a time. Nothing else has changed and I'm still using RO water.

Thanks - I wonder what the reaction is then?
 

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