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Ca:Mg:K Ratio

Happi

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15 Jan 2012
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Greeting UKAPS members, its been a while since I posted anything in this Forum, I usually post at the TPT and been busy over there. after talking to several members it appear as there is a new trend to this Ca:Mg:K ratio, there is very little information or talk about this topic, maybe we can have a good discussion about it here.

Ca:Mg:K at 3:1:0.5 ratio is what some member seems to be using or being reported, how many people here are actually using this Ratio? is this ratio based on guess work or is there a science behind it? is it also tested with valid test kits to determine if these ratio are beneficial for plants? are these ratio tested in lab to insure more Mg is being used compared to K? same for Calcium as well.

I myself do several experiments, but I was curious about this one. I was also curious if these ratio are what suppose to work best for aquatic plants, then how come ADA, Tropica, Seachem aren't using these ratios? and they have much more resources to test or investigate into this kind of stuff.
 

papa_c

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22 Jan 2013
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342
Not really sure on the ratio, I use remineralised RO at Ca 35ppm, Mg 14ppm, K 30ppm, so this would be close to 2:1:2, and dose additional 65ppm K during the week, tank is very heavily planted with healthy grow
 

dw1305

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Hi all,
Ca:Mg:K at 3:1:0.5 ratio is what some member seems to be using or being reported, how many people here are actually using this Ratio? is this ratio based on guess work or is there a science behind it? is it also tested with valid test kits to determine if these ratio are beneficial for plants? are these ratio tested in lab to insure more Mg is being used compared to K? same for Calcium as well.
My guess is that you would need to <"add more potassium (K) long term">. There is quite a lot of <"work on hydroponic crops">, and I don't see why aquarium plants should be any different.

Plants don't actually need much calcium (Ca), but many of them would have evolved in water with ~150ppm calcium, purely because that water will be ~saturated with Ca++ and HCO3- ions, from dissolved limestone. Same for magnesium (Mg) plants don't need that much of it, but it is essential for chlorophyll formation.

cheers Darrel
 

Zeus.

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Ca:Mg:K at 3:1:0.5 ratio

Well my tap water is -
142 ppm Ca
5.5 ppm Mg
?.? ppm K

So if I dose 20-30ppm K (EI dosing), then my Mg should be 40-60ppm so need to dose more Mg, then it follows My Ca should be 120-180 ppm Ca

But what is my [K] to start off with as my water company doesn't give that information :banghead: without the [K] its a rabbit hole, RO isn't an option with a 500l tank ATM.

T Barr use to talk about Ca, Mg and K ratios, but has kind off dismissed them as he has had tanks with various Ca, Mg and K ratios and they work fine in his hands.

I am sure their is a definitive answer, it just we are not on that page yet IMO
 

JoshP12

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8 Dec 2019
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527
Location
Canada
Hi all,

I am continually intrigued by this "ratio" and why it came about.

My tap is
9 Ca
2 Mg

I dose the following at water change (and I probably change 80% water weekly).
15 Ca
16 Mg
23 K

Then 15K from dosing nitrate and phosphate during the week.

Potassium (and phosphate) < directly influences > photosynthesis.
Something sticks out to me in that paper:
In hickory seedlings, as K supply reduced, ... which suggests that the major influence of K on leaf photosynthesis in hickory seedlings may be attributed to a larger mesophyll resistance and/or a lower capacity of the CO2-fixation cycle

Now, these are aquatic plants and not hickory seedlings, but the fact that potassium can impact the ability to "capture" CO2 is huge.

If we pull the plug on potassium dosing, then we can probably jam photosynthesis (probably why ADA system and F.O. dose it so liberally) . So, I am skeptical on the .5 part.

There is also probabilities to consider. If we put literally 3:1:0.5 Ca:Mg:K, then nothing will grow -- just because there just isn't enough to come in contact with the plants.
Ca:Mg:K at 3:1:0.5 ratio is what some member seems to be using or being reported, how many people here are actually using this Ratio? is this ratio based on guess work or is there a science behind it? is it also tested with valid test kits to determine if these ratio are beneficial for plants? are these ratio tested in lab to insure more Mg is being used compared to K? same for Calcium as well.

I think once it is working, we need to push the boundary. So, I should add another tsp of Mg next week at water change, keep it for a month (or a week), then do it again and see what happens.

But, to answer the question about why, I think we need some details:
1) How the plant obtains these nutrients (passive/active transport) at different parts of the root and shoot system.
2) If the plant has a mechanism to moderate its own nutrient intake regardless of the water it is in
3) If we can force the plant to uptake nutrients (probably via passive diffusion) simply with concentrations -- as a result, we would need to consider what impact Ca/Mg/K would have on either side of the plant (both in the WC and in the plant). This is kind of the opposite of 2.
4) Where the specific plant in question comes from (and as such has the evolutionary ability to grow under these circumstances).

I think that ratio-ranges are more suiting as the tank is dynamic (the ratio in the water column is constantly changing as these plants are taking up nutrients readily). Hard and fast ratios aren't going to hold.

Common quotes are
Ca 20-30
Mg >5 (I've had Mg deficiency here though and I like it higher)
K -- 20-30

The other question is the impact that Nitrate/Phosphate (now these are anions so meh) will have on these nutrient interactions ... and we stumble onto mulders.

We also need to consider the CEC of the soil. As time passes, perhaps different amounts of the Ca/Mg will be transferred in ... and what if there aren't roots yet? Or the plant is a calcifuge? Or it's an epiphyte?

It's too much.

Probably best just to dose 15/5*/20 Ca/Mg/K at water change and dose up your macros and micros and use @dw1305's floating plant method to dial in your recipe. Can always consider your tap before that too.

Then try to break it.

Josh

*I'd make that 10 ... grin.
 
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Happi

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15 Jan 2012
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I was hoping to see and hear from those who were actually using these ratios’ but I guess there aren’t many people out there who are actually using this ratio. Anyways, I personally believe that Mg seems to play more important role than the Calcium in most cases, I observed that plant will continue to grow fine even with very little calcium, but they seem to show Mg deficiency more often when Mg was low.

When using urea, there was very little calcium needed or plant didn’t show any sign of Ca deficiency under such condition, it appear as Ca was needed when NO3 became the dominate source of N.

Now days I usually maintain 1:0.5 or 1:1 K:Mg ratio, in most cases similar to Tropica and use very little Calcium. Tropica never explained how much Calcium they use or add if 100% RO water is used with their product, I tried asking them several time but no luck. Maybe they don’t even add any Calcium at all.



If anyone is interested, they can find my thread and posts on TPT as well.
 

JoshP12

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I was hoping to see and hear from those who were actually using these ratios’ but I guess there aren’t many people out there who are actually using this ratio.
Many in the UK have high calcium water -- would probably only dose 35 tbsp of Epsom Salts, if they had to ... hehe. But I think that is invaluable. In that, the systems are far too unique to extrapolate.
Anyways, I personally believe that Mg seems to play more important role than the Calcium in most cases, I observed that plant will continue to grow fine even with very little calcium, but they seem to show Mg deficiency more often when Mg was low.
I'd love to hear more about this.
When using urea, there was very little calcium needed or plant didn’t show any sign of Ca deficiency under such condition, it appear as Ca was needed when NO3 became the dominate source of N.
Thank you so much for sharing these insights. I have a hunch that EI dosed tanks require that extra GH booster due to some interactions ... have no evidence to support my hunch though --- so it is simply that. To clarify, we probably need more Calcium in EI dosed tanks than non-EI dosed tanks.
Now days I usually maintain 1:0.5 or 1:1 K:Mg ratio, in most cases similar to Tropica and use very little Calcium. Tropica never explained how much Calcium they use or add if 100% RO water is used with their product, I tried asking them several time but no luck. Maybe they don’t even add any Calcium at all.
Again, thanks for sharing this.
If anyone is interested, they can find my thread and posts on TPT as well.
Will do.

Josh
 

jaypeecee

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When using urea, there was very little calcium needed or plant didn’t show any sign of Ca deficiency under such condition, it appear as Ca was needed when NO3 became the dominate source of N.
Hi @Happi

Very interesting as I'm also interested in this Ca:Mg ratio plus I'm shortly planning to try using urea. I will report the latter at:


Returning to the Ca:Mg ratio, I couldn't find any reference to the 4:1 ratio in Diana Walstad's Ecology of the Planted Aquarium. But, I will explore further.

JPC
 

Zeus.

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Ca:Mg ratio

I think is more of Ratio of Ca:Mg ( and Ca:Mg:K) which has worked well for folks, or when folks have done well then they happen to find have a certain ratio.
Been working on the IFC calculator esp the reminerilisers and do have the Ca:Mg:K ration of TNC GH Boost if thats of any interest
1611078986549.png
 

jaypeecee

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Hi @Zeus.

Thanks for that. So, TNC GH Boost is 3 [Ca] : 1.0 [Mg] : 4.5 [K]. Wouldn't it be nice to know exactly how these figures were derived?

JPC
 

Zeus.

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1611081711193.png

Seachem Equilibrium for you also- Bit higher in [K]

Most of the commercial ferts contain very little Ca and Mg, may be its so we have to buy a remineriliser as well, why sell everything in one product when you can sell more products and it looks more comprehensive in some ways.
1611082452895.png
 

dw1305

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Hi all,
Most of the commercial ferts contain very little Ca and Mg, may be its so we have to buy a remineriliser as well, why sell everything in one product when you can sell more products and it looks more comprehensive in some ways.
This is just fantastic, you have done more than <"just deskill potion making">.

In fact I'm now worried that shadowy figures are going to appear at your door one night, make you an offer you can't refuse and tell you that if you don't stop this <"you will be sleeping with your fishes">.

cheers Darrel
 
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Hi all,

This is just fantastic, you have done more than <"just deskill potion making">.

In fact I'm now worried that shadowy figures are going to appear at your door one night, make you an offer you can't refuse and tell you that if you don't stop this <"you will be sleeping with your fishes">.

cheers Darrel
Excuse my chemistry, but I think there is reason beyond commercial gain. Ca and Mg ions are relevant to water hardness, which people want to control when keeping different types of fish and shrimp. People don’t want to be limited to a binary options of low hardness and low ‘nutrients’ or high hardness and high ‘nutrients’.
 

jaypeecee

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Hi Folks,

I may be the only user of Tropic Marin Re-Mineral Tropic* (RMT) here on UKAPS but I was informed by Tropic Marin that this product has a calcium to magnesium ratio of 3:1. This applies to both the earlier and more recent formulations of RMT.

* RODI remineralizer

JPC
 

dw1305

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Hi all,
Ca and Mg ions are relevant to water hardness, which people want to control when keeping different types of fish and shrimp. People don’t want to be limited to a binary options of low hardness and low ‘nutrients’ or high hardness and high ‘nutrients’.
Most of the commercial ferts contain very little Ca and Mg, may be its so we have to buy a remineriliser as well, why sell everything in one product when you can sell more products
I agree they <"don't need to be linked">.

In terms of calcium (Ca) and magnesium (Mg) plants have a fairly small requirement, but much of the worlds fresh water <"has them"> (and particularly Ca) in great abundance. I'm not sure the that the calcium : magnesium ration is that important. If I was an RO user I might go for about 5 ppm of each.

Because we have <"hard, good quality tap water"> I use that as my Ca and dKH source and <"I add a bit of Epsom Salts (MgSO4.7H2O)"> to add Mg (and a small additional amount of dGH)

I can think of plenty of situations where you have low nutrients and high dKH/dGH. In freshwater it could be <"Lake Tanganyika">, a chalk stream etc.

In the UK we usually regard dGH/dKH as linked, because most of our hardness is from limestone (calcium carbonate (CaCO3)) and that <"provides 1 : 1 dGH / dKH">.

If I kept Lake Tanganyika Cichlids I'd still use the <"Duckweed Index">. It is one of its great advantages that it works across the whole gamut of freshwater types.

cheers Darrel
 
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Zeus.

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jaypeecee

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Hi Folks,

It suddenly dawned on me last night that perhaps the exact [Ca]:[Mg] ratio and absolute concentrations are much more important to fish and other livestock but less important to plants. Perhaps everyone else was already one step ahead of me but I can live with that! It would also appear that I started a thread almost two years ago on the subject of water column electrolytes:


JPC
 

Mortis

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17 Jun 2009
Messages
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I have very soft water and want to increase my Calcium dosing. I already dose some Mg mixed with my Macros and after every WC I dose a GH booster which is a mix of MgSO4 and CaSO4. CaSO4 is sparingly soluable but should be fine in the volume of tank water. Is there an alternative Ca salt I could use that mixes stably with MgSO4 ? Ive forgotten my chemistry. I have CaCl2 but that wont work with MgSO4. What else could I use ?
Should I replace KNO3 in my macros with CaNO3 instead ?
 
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