DIY all in one fertiliser solution going cloudy

[Rapayich]

I have been messing around with making my own all-in-one fertiliser mix over the past few months but can't seem to get it right. In my solutions I am using:

KNO3
KH2PO4
MgSo4
DTPA Iron 11%
Copper sulphate (Unchelated)
Manganese sulphate (Unchelated)
Boric Acid (Unchelated)
Zinc Sulphate (Unchelated)
Sodium Molybdate (Unchelated)
Potassium Sorbate
Ascorbic Acid
RO Water

Before adding the salts I ensure the water has been acidified to about 2.5pH. I also ensure that the macro and micro solutions are fully dissolved before combining. The solution remains clear for about 2 weeks but then goes cloudy. Note that no precipitate can be seen but it definitely goes cloudy throughout the whole solution. Does anyone have suggestions regarding this issue. Maybe the cloudiness is not a problem and is moreso some sort of bacterial buildup? My RO unit is very old but can still produce water around TDS 5. Solutions are kept at room temp and in a dark container away from sunlight.

Cheers!

 

[Happi]

For some reason I had assumed that DPTA 11% would do the same as DTPA 7% but to a lesser degree. This is an eye opener and the PH drop was rather significant.

I believe some of the EDTA also lower the PH as well. I will have to test them in my free time to confirm that.

 

[Hanuman]

I believe some of the EDTA also lower the PH as well. I will have to test them in my free time to confirm that.

It does but to a lesser degree than 11% DTPA. It dropped 0.4 PH points. I also noticed it takes more time to dissolve.

Fe 13.2% EDTA

 

[Zeus.]

For some reason I had assumed that DPTA 11% would do the same as DTPA 7% but to a lesser degree. This is an eye opener and the PH drop was rather significant.

Intersting, is that for the same increase in [Fe]?
Yet after a quick google they seem to be the same chemical
Maybe @X3NiTH can shed some light on this

 

[Hanuman]

Interesting, is that for the same increase in [Fe]?

No, I just grotesquely eye balled a similar amount in the spoon. I was just looking for the PH to either go up or down.

Yet after a quick google they seem to be the same chemical

Yes I can't explain why this is happening. Let's see what X3nith has to say about this.

 

[Zeus.]

With the 7% giving a less of a pH drop surgests there is another element bonding to some of the DTPA with maybe a higher bond strength so isn't so soluble and resulting is less of a pH dtop. Stab in the dark 🤣

 

[_Maq_]

I am interested to know why it is that we can’t make these solutions stable long term? Is it a certain ingredient we can’t get access to or just our equipment and procedures?

There are several problems here.
First and foremost, it's chelated iron. Iron is always unstable in solutions. Besides, all chelators are organic acids (artificial but still organic). That means that bacteria and fungi can digest them.
Ascorbic acid is used as an reducing agent (antioxidant). It makes sense if keeping iron in reduced state, i.e. divalent. Bacteria love ascorbic acid. As well as citric acid. Glutaraldehyde is sometimes used as a conservant because it's poisonous.
Anyway, there's no way to keep dissolved chelated iron stable for long. Keeping it in fridge helps. Still, sooner or later it degrades.
Then there's the mess with other salts. They all dissociate in water and cations and anions may recombine to produce poorly soluble salts. Danger is increased when phosphates (anions) are combined with transition metals (cations - Fe, Mn, Zn, Cu, Ni).
There's a good side to that: No matter in which form you add nutrients - even in an 'inaccessible' one - plants hand in hand with microbes will find their way. But! - it takes time. What does it mean? You can use unchelated iron, for example, and plants will find out and take it up. Yet not instantly, the effect is long-term. Besides, a large portion of such an iron will end up wasted within your filter. Often together with phosphorus, and other micronutrients.

The bottom line is that we - laymen - should not attempt to make all-in-one solutions. There are too many risks it would not work as intended. After all, if you are a dedicated plant-grower, you should ENJOY fertilizing, adjusting your formulas and observing the results, and not to seek a one-for-all solution. This hobby does not respond well to one-for-all solutions.

 

[Aqua sobriquet]

Will definitely do that, did not realise there was a special order for the nutrients. Thank you

I am interested to know why it is that we can’t make these solutions stable long term? Is it a certain ingredient we can’t get access to or just our equipment and procedures? I have noticed some commercial ferts use citric acid as opposed to ascorbic and some use both. A quick Google suggests citric acid is quite a good chelator. Could this be key in making the solutions viable for longer?

I will also be disinfecting containers from now on. Hopefully this helps.

Yes agreed. I’ve seen some Tropica fertiliser that’s been on the shelf a long time judging by the dust on them and they were perfectly clear and sold in transparent bottles? What’s the secret? It’s also a very bright Green compared to many others.

 

[Rapayich]

There are several problems here.
First and foremost, it's chelated iron. Iron is always unstable in solutions. Besides, all chelators are organic acids (artificial but still organic). That means that bacteria and fungi can digest them.
Ascorbic acid is used as an reducing agent (antioxidant). It makes sense if keeping iron in reduced state, i.e. divalent. Bacteria love ascorbic acid. As well as citric acid. Glutaraldehyde is sometimes used as a conservant because it's poisonous.
Anyway, there's no way to keep dissolved chelated iron stable for long. Keeping it in fridge helps. Still, sooner or later it degrades.
Then there's the mess with other salts. They all dissociate in water and cations and anions may recombine to produce poorly soluble salts. Danger is increased when phosphates (anions) are combined with transition metals (cations - Fe, Mn, Zn, Cu, Ni).
There's a good side to that: No matter in which form you add nutrients - even in an 'inaccessible' one - plants hand in hand with microbes will find their way. But! - it takes time. What does it mean? You can use unchelated iron, for example, and plants will find out and take it up. Yet not instantly, the effect is long-term. Besides, a large portion of such an iron will end up wasted within your filter. Often together with phosphorus, and other micronutrients.

The bottom line is that we - laymen - should not attempt to make all-in-one solutions. There are too many risks it would not work as intended. After all, if you are a dedicated plant-grower, you should ENJOY fertilizing, adjusting your formulas and observing the results, and not to seek a one-for-all solution. This hobby does not respond well to one-for-all solutions.

I am attempting to make an all in one fertiliser solution because it is enjoyable for me . I know it is possible as many companies and other hobbyists have done it before. It has certainly been challenging for me but rewarding as I have seen progress.

Does the potassium sorbate not prevent the mold and bacteria? At least that’s how I have interpreted it in my readings.

Also unsure what you mean by chelated iron always being unstable in solutions. I can’t see how this can be the case if we see so many all in one fertilisers on the market. From memory the DTPA iron I am using says it is stable in solutions between 1.3 and 7 ph.

The transition metals, yes I definitely think I have a problem with them reacting with phosphate. I believe this may be the reason I see clouding eventually. I may need to switch to chelation of some of these metals.

 

[Rapayich]

Yes agreed. I’ve seen some Tropica fertiliser that’s been on the shelf a long time judging by the dust on them and they were perfectly clear and sold in transparent bottles? What’s the secret? It’s also a very bright Green compared to many others.

I have read about the bright green colour somewhere but really can’t remember. Either way it must be doable. I’m pretty sure 2hr aquarist ferts have a shelf life of 3 years.

 

[Hanuman]

I am attempting to make an all in one fertiliser solution because it is enjoyable for me . I know it is possible as many companies and other hobbyists have done it before. It has certainly been challenging for me but rewarding as I have seen progress.

Does the potassium sorbate not prevent the mold and bacteria? At least that’s how I have interpreted it in my readings.

Also unsure what you mean by chelated iron always being unstable in solutions. I can’t see how this can be the case if we see so many all in one fertilisers on the market. From memory the DTPA iron I am using says it is stable in solutions between 1.3 and 7 ph.

The transition metals, yes I definitely think I have a problem with them reacting with phosphate. I believe this may be the reason I see clouding eventually. I may need to switch to chelation of some of these metals.

There is absolutely no problem in doing AIO solutions. The only thing is that you need to make a weak solution rather than wanting to match the concentration of commercial products. I am currently using a clone of APT3 that I prepared over a 3 months ago and the solution is still clear. All my traces are unchelated except for the iron which I use FE DTPA 11%.

 

[Rapayich]

N

There is absolutely no problem in doing AIO solutions. The only thing is that you need to make a weak solution rather than wanting to match the concentration of commercial products. I am currently using a clone of APT3 that I prepared over a 3 months ago and the solution is still clear. All my traces are unchelated except for the iron which I use FE DTPA 11%.

Nice! Did you just use ascorbic acid and potassium sorbate?

 

[Hanuman]

N

Nice! Did you just use ascorbic acid and potassium sorbate?

Yes, as stipulated by the IFC calculator.

 

[_Maq_]

Does the potassium sorbate not prevent the mold and bacteria?

It is said so. About a half year ago, I've attempted to fight fungi in my tank with potassium sorbate. I've got a fine bacterial bloom...

Also unsure what you mean by chelated iron always being unstable in solutions. I can’t see how this can be the case if we see so many all in one fertilisers on the market

(1) Let's not take for granted that all vendors of such fertilizers are honest and good chemists.
(2) If they are, they may apply methods of which we do not know, or for which advanced processing is required.
It's quite difficult to prove them wrong as long as given element is present in the solution. If you detect iron ions and EDTA, it does not mean necessarily that Fe-EDTA is there.
In principle, any piece of rock containing given element can serve as a fertilizer. It's just a matter of time till it takes the form available to plants. It may happen instantly, or in thousand years. Still, the element is there.

The transition metals, yes I definitely think I have a problem with them reacting with phosphate. I believe this may be the reason I see clouding eventually. I may need to switch to chelation of some of these metals.

Chelates are not forming permanent bonds. In solution, they release the metal ion and capture the same one or another one in short periods of time. (If it didn't work like that, 'permanently' bound metal ions would be inaccessible to the plants, because plants take up metals as ions!) Therefore, you cannot avoid formation of poorly soluble phosphates by chelating the metals.

I have read about the bright green colour somewhere

Bivalent iron is green, in contrast to trivalent iron, which is yellow-red-brown depending on concentration.

 

[Courtneybst]

Few questions:
1. Does the chelated trace contain Fe already?
2. What is the container size?
3. What is the brand of the chelated traces and Fe?
4. What is the tank volume?

I'm trying to plug your numbers in the IFC calculator to see if anything is off.

Hi mate, these are the deets;

1. It does contain Fe, EDTA
2. Container size is 1L
3. Chelated trace is from Aquarium Plant Food UK and the DTPA is from Aqua Plants Care
4. Tank maximum volume is 300L, but significantly less with the huge bit of wood, although I am dosing as if it is 300L.

 

[Happi]

Yes agreed. I’ve seen some Tropica fertiliser that’s been on the shelf a long time judging by the dust on them and they were perfectly clear and sold in transparent bottles? What’s the secret? It’s also a very bright Green compared to many others.

the bright green color could be due to the iron being in ferrous stage or they simply add dye to change the color. i have some stock solution sitting in the garage for many years which has seen both hot and cold days and they are still clear. i also have seen some solution going bad even while using Ascorbic acid and Potassium Sorbate. the good overall alternative is Sodium Benzoate if you want to keep the solution clear for long term. I would avoid adding Ascorbic acid with the Sodium Benzoate if you choose to go this route.

 

[Hanuman]

Hi mate, these are the deets;

1. It does contain Fe, EDTA
2. Container size is 1L
3. Chelated trace is from Aquarium Plant Food UK and the DTPA is from Aqua Plants Care
4. Tank maximum volume is 300L, but significantly less with the huge bit of wood, although I am dosing as if it is 300L.

And I forgot to ask what is the dosing regime? quantity and frequency?
What % is the Fe from Aqua Plants Care?

 

[Hanuman]

i also have seen some solution going bad even while using Ascorbic acid and Potassium Sorbate.

Yes it's not bullet proof. I've seen the same in some batches but I attribute it to contaminated or poorly clean containers among other reasons. For instance the current batch I am working on is still very much clear after 3 months. However, the previous one, which was not even an AIO developed mold or whatnot. I think the quality/grade of the compounds we use is also largely responsible. Some are simply low grade and contain impurities/pathogens to start with, which makes the process even more prone to mold or bacterial development.

the good overall alternative is Sodium Benzoate

What would be the recommended dosage/L?

@X3NiTH what's your view on this?

 

[Rapayich]

the bright green color could be due to the iron being in ferrous stage or they simply add dye to change the color. i have some stock solution sitting in the garage for many years which has seen both hot and cold days and they are still clear. i also have seen some solution going bad even while using Ascorbic acid and Potassium Sorbate. the good overall alternative is Sodium Benzoate if you want to keep the solution clear for long term. I would avoid adding Ascorbic acid with the Sodium Benzoate if you choose to go this route.

Maybe those solutions that have gone bad are more concentrated than the ones that have lasted?

Is sodium benzoate somehow better? Why is it that the two cannot be used together?

 

[Happi]

What would be the recommended dosage/L?

I add about 0.3 gram for 500 ml solution

 

[Happi]

Maybe those solutions that have gone bad are more concentrated than the ones that have lasted?

Is sodium benzoate somehow better? Why is it that the two cannot be used together?

Still had some simple solution go bad on me while using ascorbic acid and some of them even used high quality chemicals.

Sodium Benzoate and Ascorbic Acid risk factors