Solufeed TEC-SF usage experience

[X3NiTH]

@Vsevolod Stakhov is probably experiencing whatever I experience from time to time while using Asrobic acid. I think i described this issues in one of the thread. my only guess is that the more Asrobic acid we add, it break down the Chelate and possibly precipitate the Iron and other elements, this occurred even while using a pure Distilled water to make the solution.

Fundamentally what is happening is that increased acid addition is changing the solution charge equilibrium toward an increase in protonation, the solution therefore is out of charge balance and as such there will be reactions between the elements within the solution to bring it back into balance even when all compounds are below their solubility threshold. More complex acids like Ascorbic and Acetic introduce carbon into the equation which will form part of reaction products to balance the charge, this would increase the chances of carbonate compound formations which can be fairly insoluble, a simple acid like HCl reduces the complexity of the charge balance equation and if compounds are formed they will be more likely chlorides which are very soluble so the chances for precipitative effects are much more reduced.

You can calculate the charge balance for a pH moderated solution of chosen compound molar concentration beforehand to reduce the likelihood of precipative effects but it becomes a very Complex Equilibrium Equation as you add more compounds in differing molar concentration.

The document below is an exceptional read and has all the equations within to calculate the above and so much more!

W. M. White Geochemistry Chapter 6: Aquatic Chemistry

🙂

 

[X3NiTH]

It is important to use Distilled or RO or Rain Water. Group II ions, Ca & Mg, unless chelated, will replace Iron and other Transition Metals from chelation.

Here is the Affinity graph for EDTA.



🙂

 

[dw1305]

Hi all,

The document below is an exceptional read and has all the equations within to calculate the above and so much more!

W. M. White Geochemistry Chapter 6: Aquatic Chemistry

That is very useful, thank you.

cheers Darrel

 

[Happi]

Bit off topic but I have a solution that is made out of CaNO3, Mgno3, Kno3, urea, kcl, Traces EDTA based, Fe EDTA, Fe DTPA, Fe EDDHA.

No PO4 added to this, it's also free of Sulphate, it was made in May 25th, 2020 and stored in the garage where it has seen both hot and cold days. The solution is quite stable without any prectipation, it's wine color. I believe the EDDHA and DTPA is doing the major work here.

Note: the Bottle looks dirty with dust, debris etc attached to it on the outside, don't assume that as a prectipations.

 

[Vsevolod Stakhov]

Here is the Affinity graph for EDTA.

Well, Ca/Mg EDTA chelates are stable merely in alkaline PH (that's why our GH test has to establish alkaline conditions first). I think the point was that bicarbonates of alkaline metals can set the overall alkaline reaction of a water sollution (as they are the salts of a weak acid and a strong hydroxide). So if you want to add Fe or other heavy metal salt to be chelated, you need to ensure that the PH is suitable for that. For example, addition FeSO4 to 4NaEDTA sollution will just produce perciptation of the Fe(OH)2, whilst addition 4NaEDTA to FeSO4 will produce FeEDTA- as expected (because FeSO4 is an acidic salt that has PH~3).

I've also investigated my initial situation with ascorbic acid. The only hypothesis I have is indeed that there was too low PH in my sollution. EDTA and DTPA as acids are insoluble in water. And we also know that Solufeed chelates do not have Na cations in the external sphere but NH4 ones. NH4+ is a very weak alkali comparing to Na+, so presumably the PH of the sollution was too low to move EDTA/DTPA to unsoluble state. I don't know what happens to the internal sphere (where Fe ion is placed) during this process, I'm afraid. However, removing acorbic acid seems to slow down this process slightly.

The colour is still changing from bright green to yellow/brown (this might just be related to Fe2+ -> Fe3+ oxidation). And I still see some perciptation unfortunately. On the other hand, JBL tests still shows that there is enough iron in soluble state in both tank water and in the fertiliser.

 

[Oldguy]

Solufeed chelates do not have Na cations in the external sphere but NH4 ones.

EDTA does not contain NH4 but has amine groups that are covalently bonded to the resultant ligand that partially or fully encapsulates the central metal ion that has been chelated. These amine groups are not ionic and are stable even when the central metal ion is removed or replaced.
The Na or K ions (dependent on formulation) just balance the resultating net ionic charge of the chelated complex.

 

[Vsevolod Stakhov]

The Na or K ions (dependent on formulation) just balance the resultating net ionic charge of the chelated complex.

I'm talking about the external sphere of a chelate. It has either H+ or Na/K/NH4 cations or some combinations (like 2Na2H EDTA). As far as I know, Solufeed uses NH4 instead of Na to balance the external sphere, but I might be wrong here and there are K+ cations there (but definitely not Na, as it is Sodium free mix).

 

[X3NiTH]

The Solufeed mentioned above isn’t using Sodium EDTA, it’s either Diammonium EDTA or Potassium EDTA depending on the Ion to be chelated, blended trace mix will be using a combination of them both.

This is what PubChem has to say about Edetate Diammonium and Edetate Dipotassium.

Here’s DOW chemicals Technical Specs for their Diammonium EDTA, Tech Specs for their Potassium EDTA are not available.




I’ll bet that Solufeeds formulation will be identical.

Take note of the pH of solubility and the fact that Ammonium is the Protonated form of Ammonia and that if this is used in ranges outside it’s solubility it could be problematical in above neutral pH conditions (?Ammonia Toxicity) if overdosed accidentally into an aquarium, the fear may be unfounded but I would still be aware.

🙂

 

[Vsevolod Stakhov]

As far as I know, Solufeed uses NH4 instead of Na

Well, it seems this is not correct for some trace elements. According to another mix they use the following chelates:
CuNH4EDTA
FeKEDTA
Mn2KEDTA
Zn2KEDTA

However, for DTPA they sell the only one sodium free chelate: ferric ammonium DTPA. So my assumption that the external sphere ions are (mostly) NH4+ seems to be correct after all.

 

[X3NiTH]

So my assumption that the external sphere ions are (mostly) NH4+ seems to be correct after all.

Yup!

🙂

 

[Happi]

I believe X3NiTH and Oldguy is referring to this, most Chelate will have the N in the amine groups which is actually utilized by the plants quite well. EDTA also contain Na while DTPA doesn't, some Hydroponic people don't use Fe EDTA but rather prefer Fe DTPA because Fe EDTA is toxic and is used as Herbicides. Fe HEDTA used for killing weed:​

Using iron-based herbicides for alternative weed control. - My Green Montgomery​

 

[Happi]

Well, it seems this is not correct for some trace elements. According to another mix they use the following chelates:
CuNH4EDTA
FeKEDTA
Mn2KEDTA
Zn2KEDTA

However, for DTPA they sell the only one sodium free chelate: ferric ammonium DTPA. So my assumption that the external sphere ions are (mostly) NH4+ seems to be correct after all.

in theory these would be better for our aquatic plant with addition of NH4 and no Sodium Compared to some Chelate such as Sodium based EDTA. send some to USA for me 🙂

 

[Oldguy]

NH4+ seems to be correct after all.

My stock of Iron EDTA has sodium cations to 'balance' the anion EDTA complex.

Did not know that ammonium cations were now being used but were aware that potassium cations were available.

Bought my stock over 15yrs ago when its main application was as a folia feed for top fruit, especially the one with trace elements combined in the mix. The later was not then available in the small kg bags.

Like this forum always learning new things and being updated on new products.

 

[Vsevolod Stakhov]

in theory these would be better for our aquatic plant with addition of NH4 and no Sodium

Yes, but even on the EI Fe addition as 0.5ppm per week, the amount of counter-ions is quite negligible, for either Sodium or NH4/K+ (less than 0.5ppm due to molar weight).
I have measured the PH of the browned sollution and it seems to be around 7-8 (harder to say more precisely as it is coloured itself, so I have to use either test strips or try to guess using liquid tests). The Fe there is still solluble and detectable but I would definitely prefer to make a fresh sollution more frequently, as it seems to be less stable than EDDHA added mix. On the other hand, I like that there is no more pink colouring in the water, and the plants look good after all:

 

[Vsevolod Stakhov]

I have recently observed a strange effect after adding this feriliser that I personally could not explain at all. So I add Solufeed TEC-SF to my 3 tanks to level of 0.1ppm Fe 3 times per week (combining with FeDTPA 0.1 * 2 times per week). However, last time I've added this combination to my malawi tank, all fishes were struggled to breath showing clear signs of low oxygen: gasping air, frequent breathing etc. I've immediately increased aeration and changed around 10% of water from tap, so it was clearly a lack of dissolved oxygen somehow.

But other two softwater (KH=1..4) tanks were totally fine, it was only cichlids tank that suffered. It is different as it uses pure tap water with KH=12 and GH=18 (110ppm Ca). I'm also observing that the water during water changes has somehow turquoise or aquamarine colour . This colour is also quite unique for this tank, and it is not caused by algae or something - the water is crystal clear. Softwater tanks' water does not have such a colour, just in case.

So I really cannot answer a question about how an addition of the micro-elements could cause oxygen depletion. The chelates are not "easy" organic, such as gluconate, so it might be something else (however, even most simple organic would not cause that fast oxygen depletion). I also cannot explain the colour of the water at all.

Of course, that could be a coincidence (and it's likely so), but probably someone has any thoughts on that before I try to dose that fertiliser one more time in that tank.