Latest insights on Calcium

[dw1305]

Hi all,

I am really benefiting from these chemistry lessons.

I didn't know why FeEDTA is ineffective at higher pH levels, so it is useful to know why and the reason for it,

cheers Darrel

 

[X3NiTH]

This is the Affinity chart for EDTA.

EDTA is environmentally persistent (only seen to be dismantled by a species of bacteria that grows in the pond waters of nuclear power stations), when it looses its bond to the metal ion it is chelated with either via plant uptake, pH effect or photolysis then the next ion to be chelated will be dependant on presence and pH. If the pH is low then it can re-uptake heavier metal ions, if the pH is above neutral and out of range for FeEDTA then it will preferentially bind with Calcium when the Iron is dropped.

 

[arcturus]

no it's driven by EI philosphy. another example is K dosage. because plants always use N more than K. which means in theory, no3:k ratio of 4:1 should be more than sufficient. yet, EI users regularly add same or more amount of K compared to No3.

But isn't this a consequence of the salts commonly used with EI, especially because this regime is often used with RO water? The common fertilization and remineralization salts tend to favour K. It is possible to avoid high values of K, but this would lead to higher amount of Ca and/or Mg. These common salts will always introduce an amount of K, Ca, or Mg significantly above what is considered sufficient.

 

[arcturus]

View attachment 181778
mostly based on terrestrial plant data. but above, is critical concentration of nutrients in Elodea nuttalli, you can see the ratio is close to 3:1. my tank is dosed to 18ppm Ca and 6ppm Mg ~4dgh. a good middle ground between keeping water collumn dosing minimal and shrimp happy i think. @Yugang

But this table only shows that the plant is storing Ca and Mg at a 3:1 ratio. It says nothing about the availability of these nutrients outside the plant. Especially, it does not say that a 1:1 or any other ratio in the environment is detrimental to plant or favours the plant.

 

[MichaelJ]

Hi all,

I didn't know why FeEDTA is ineffective at higher pH levels, so it is useful to know why and the reason for it,

cheers Darrel

Quote: "Above the pH of 6.5 nearly 50% of the iron is unavailable". ... thats the one that is puzzling to me... What exactly does it mean? is it "instantly" unavailable ? what roles does time play here? How fast does plants mop up the Fe vs. the timeframe when the Fe becomes unavailable etc. ? Is it really something we have to worry about?

In the past I have run both my densely planted tanks very successfully in the 7.2-7.6 pH ange dosing ~1.0 ppm EDTA Fe and never suffered from Iron deficiencies. (I'm currently closer to ~6.5 after starting with botanicals @ low KH).

Regards,
Michael

 

[plantnoobdude]

But isn't this a consequence of the salts commonly used with EI, especially because this regime is often used with RO water? The common fertilization and remineralization salts tend to favour K. It is possible to avoid high values of K, but this would lead to higher amount of Ca and/or Mg. These common salts will always introduce an amount of K, Ca, or Mg significantly above what is considered sufficient.

I mean, Cano3. 20ppm no3 will get ~6ppm Ca, from there add some kh2po4 and top up k with some k2so4.

 

[arcturus]

I mean, Cano3. 20ppm no3 will get ~6ppm Ca, from there add some kh2po4 and top up k with some k2so4.

But with RO water this would lead to an dGH ~0.9° (and zero dKH). Same if using MgNO3. If you want to target a dGH of ~6° then you need to start adding Mg and Ca, leading to Ca and Mg (and Cl or SO4) values way above the "sufficient".

 

[plantnoobdude]

But this table only shows that the plant is storing Ca and Mg at a 3:1 ratio. It says nothing about the availability of these nutrients outside the plant. Especially, it does not say that a 1:1 or any other ratio in the environment is detrimental to plant or favours the plant.

the amount being stored is different to critical concentration. the amount that the plant is storing Ca and Mg is at a very different ratio
around 3:2. elements found inside plants are not particularly useful, especially because of luxury uptake.

critical concentration is the collumn on the left, which aligns very closely to 3:1 ratio. critical concentration is defined as
"Critical level or concentration is a term that is common in both soil and plant analysis. It is usually defined in plant analysis as the level that results in 90% of maximum yield or growth"

Plant Analysis - Nutrient Management

Plant analysis refers to the measurement of essential nutrient content of plant tissue by laboratory analysis. There have been many advances in plant analysis.

www.cropnutrition.com

such ratios are not particularly useful untill you get into toxicity ranges or other issues, but if you are trying to add as little as possible and keep the water collumn lean then it is advisable to use such a ratio.

"Especially, it does not say that a 1:1 or any other ratio in the environment is detrimental to plant or favours the plant."

i was just explaining why the 3:1 ratio is commonly used. im not saying 3:1 ratio is perfect for every tank and plant, just why people choose to use it quite a lot.

i answered this question by Yugang.
"Mg is nearly always earmarked as an essential nutrient, while for Ca most dosing schemes do not even set a target. Why would we dose Ca 2-3 times more than Mg?"
I said it's mostly because of terrestrial plant data.

 

[arcturus]

the amount being stored is different to critical concentration. the amount that the plant is storing Ca and Mg is at a very different ratio
around 3:2. elements found inside plants are not particularly useful, especially because of luxury uptake.

critical concentration is the collumn on the left, which aligns very closely to 3:1 ratio. critical concentration is defined as
"Critical level or concentration is a term that is common in both soil and plant analysis. It is usually defined in plant analysis as the level that results in 90% of maximum yield or growth"

My point is that it is the concentration of the nutrient in the plant tissue, not in the environment. Is there a correlation between the concentration of nutrient in the environment and that in the plant tissue? If we have a 1:1 ratio in the environment the plant may end up storing those two elements in whatever ratio (assuming we are not in the deficiency range).

 

[plantnoobdude]

My point is that it is the concentration of the nutrient in the plant tissue, not in the environment.

well, the numbers above are the minimum amount of nutrients plants must have to grow unrestricted. if the numbers go above the numbers the plant will store the excess inside plant tissue due to luxury uptake. i do not know the exact relationship but i assume if the amount of nutrients in the environment above critical concentration is 1:1 the plant will store it in plant tissue as one to one.

But with RO water this would lead to an dGH ~0.9° (and zero dKH). Same if using MgNO3. If you want to target a dGH of ~6° then you need to start adding Mg and Ca, leading to Ca and Mg (and Cl or SO4) values way above the "sufficient".

that is the entire point right? keeping nutrients low, seeing if lower amounts are sufficient. dgh of 6 is way above what is needed, that is the point of EI. unless you use inert sub and full rodi water with no so4 and cl then it is very unlikely to see cl, so4 deficiency.

 

[X3NiTH]

"Above the pH of 6.5 nearly 50% of the iron is unavailable". ... thats the one that is puzzling to me... What exactly does it mean? is it "instantly" unavailable ? what roles does time play here?

This is the Graph you are looking for.

 

[X3NiTH]

I should point out that that’s not the whole picture because it doesn’t take into account de-chelation through irradiance which will occur any time the tank lights are on, here’s a comparison of FeEDTA and FDTPA under irradiance.

 

[Yugang]

that is the entire point right? keeping nutrients low, seeing if lower amounts are sufficient. dgh of 6 is way above what is needed, that is the point of EI

with regard to Ca deficiency in plants, are we in agreement that:

3-5 ppm Calcium in the water column is generally sufficient, or even preferred, for aquarium plants.
- Some exceptions for hard water plants.
- Irrespective of lighting, CO2, Mg and other nutrient dosing method.
- This is not taking into account the requirements of invertebrates and fish.

 

[X3NiTH]

I would suggest that the minimum amount of Ca needed would correlate with the maximum amount available in rain, it’s a tough life but some plants have to live it!

 

[Happi]

@MichaelJ​

look into "Haifa Cal Prime 17-0-0 calcium nitrate" if you want better version of Cano3. Haifa Cal Prime 17-0-0 calcium nitrate fertilizer 55 lb. -AO

 

[MichaelJ]

This is the Graph you are looking for.

View attachment 181839

Hi @X3NiTH Brilliant! Now, that curve seems like a dead giveaway that the choice of EDTA is not really an issue even at relatively high pH provided that you compensate by overshooting a bit on the weekly dosing (which we are all probably doing already...).

I should point out that that’s not the whole picture because it doesn’t take into account de-chelation through irradiance which will occur any time the tank lights are on, here’s a comparison of FeEDTA and FDTPA under irradiance.

View attachment 181843

I am not quite sure how to interpret these two curves?

Cheers,
Michael

 

[MichaelJ]

@MichaelJ​

look into "Haifa Cal Prime 17-0-0 calcium nitrate" if you want better version of Cano3. Haifa Cal Prime 17-0-0 calcium nitrate fertilizer 55 lb. -AO

Thanks @Happi I'll look into it!

Cheers,
Michael

 

[Happi]

Thanks @Happi I'll look into it!

Cheers,
Michael

the calculation would be different from any other Cano3, but here it is just in case:

500 ml, 20 ml per 50 gallon
20.135 gram Haifia Cal Prime

Ca 1
Total N 0.723
N-NO3 0.71
N-NH4 0.01276

almost 7.9 gram less compared to other CaNO3

 

[MichaelJ]

Why would we dose Ca 2-3 times more than Mg?

That is a very good question @Yugang. When you look at natural habitats it doesn't seem like Mother Nature is being excessively caught up in ratios.... for instance Chemistry of different amazonian water types. shows waterways with anything from 1:1 to 8:1 with regards to Ca:Mg contents. (but there seems to be a trend there around ~4:1) ... as a matter of fact it seems like Mother Nature is following a pretty hardcore homeopathic dosing regime

Cheers,
Michael

 

[Happi]

Mother nature: