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Saltpetre for macros?

MrClockOff

MrClockOff

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Hey!
I hope everyone is well and having great Easter break.
Just wanted to check something with you. I did run out of potassium nitrate recently (old batch from AquariumPlantFood) and restocked with saltpetre from Amazon https://amzn.eu/d/1n3Ar56. It does say potassium nitrate on the packaging.
Today when I was cleaning macro container for 3rd batch using new salpetre I noticed unusual milky residue inside the container and on the feed tube. It was thin, solid layer of something.
Does anyone have any clues what could participate like that?

I’m using 500ml of RO water, 20.96g of KNO3, 3.19g of KH2PO4, 11.74g of MgSO4.7H2O and 5ml of Florish Excel (to kill mold)

Never seen anything like that before

Cheers
 
It's odd, I've been mixing all these ferts with tap water for about 2yrs, and recently got precipitation. Not sure what exactly falls out of solution but it's not potassium or nitrate. More than likely magnesium, or a reaction of Mg with something else like mould.
 
MichaelJ said:
How do you mix it and with what? And what temperature do you store it at? KNO3 is very soluble in water (300g/L @ 20C), but quite temperature dependent. Perhaps the residue is crystallized KNO3?

Cheers,
Michael
Click to expand...
I mix it in RO water at room temperature by shaking the container as long as it takes until all salt crystals fully dissolve (disappear). I keep it only for 3 weeks at room temperature in the aquarium cabinet in darkness. After 3 weeks I prepare new batch. Room temperature swings between 19c and 23c

Cheers
 
John q said:
It's odd, I've been mixing all these ferts with tap water for about 2yrs, and recently got precipitation. Not sure what exactly falls out of solution but it's not potassium or nitrate. More than likely magnesium, or a reaction of Mg with something else like mould.
Click to expand...
Yeah, exactly, all plants looking healthy so far too. So not sure what is that. The only new thing is that new potassium nitrate.
 
MrClockOff said:
I mix it in RO water at room temperature by shaking the container as long as it takes until all salt crystals fully dissolve (disappear).
Click to expand...

Ok not temperature related then ... hmmm... Just straight up RO water and KNO3, and nothing else - not exceeding the solubility limit ? ... the only thing I can think of is impurities in the KNO3 I suppose, but it seems unlikely to have an impact given that it's 99.5% grade. Common impurities in bulk KNO3 are such things as clay btw.

Cheers,
Michael
 
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I always have a small amount of crystaline deposit when I mix up my macro solution. Have had ever since I used KNO3 from APFUK. Prior to that I had a batch from TNC and didn’t have that issue.
 
MichaelJ said:
Ok not temperature related then ... hmmm... Just straight up RO water and KNO3, and nothing else - not exceeding the solubility limit ? ... the only thing I can think of is impurities in the KNO3 I suppose, but it seems unlikely to have an impact given that it's 99.5% grade. Common impurities in bulk KNO3 are such things as clay btw.

Cheers,
Michael
Click to expand...
Apologies for misunderstanding but complete macros batch recipe is:
I’m using 500ml of RO water, 20.96g of KNO3, 3.19g of KH2PO4, 11.74g of MgSO4.7H2O and 5ml of Florish Excel (to kill mold)

So it’s not just RO and KNO3
 
I'm no expert but I wouldn't put Flourish Excel in with the Macros, I don't know the possibilities of potential reactions just instinct tells me. Potassium Sorbate is cheap enough.
 
bazz said:
I'm no expert but I wouldn't put Flourish Excel in with the Macros, I don't know the possibilities of potential reactions just instinct tells me. Potassium Sorbate is cheap enough.
Click to expand...
I read once where Seachem claimed that Excel is neutral for their fertilisers. Which makes sense especially if someone using Excel as substitute for regular CO2 setup in combination with fertilisers on daily basis. So hoping it’s still true statement. Also is excel only stable for 24h?
 
MrClockOff said:
Apologies for misunderstanding but complete macros batch recipe is:
I’m using 500ml of RO water, 20.96g of KNO3, 3.19g of KH2PO4, 11.74g of MgSO4.7H2O and 5ml of Florish Excel (to kill mold)

So it’s not just RO and KNO3
Click to expand...

Sorry, my bad. But still, the only known variable that changed is the new batch of KNO3, so I would say it's probably something (impurities) with that batch that causes the precipitation. But who knows.

Tim Harrison said:
morphic resonance
Click to expand...
good one. :lol: ...Well, Spooky action at a distance is real... - See Bell's Theorem on quantum entanglement.

Cheers,
Michael
 
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