# Ca:Mg:K Ratio



## Happi (18 Dec 2020)

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.


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## papa_c (18 Dec 2020)

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


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## dw1305 (19 Dec 2020)

Hi all,


Happi said:


> 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


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## Zeus. (19 Dec 2020)

Happi said:


> 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  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


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## JoshP12 (20 Dec 2020)

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.


Happi said:


> 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 (21 Dec 2020)

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.


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## JoshP12 (23 Dec 2020)

Happi said:


> 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.


Happi said:


> 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. 


Happi said:


> 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. 


Happi said:


> 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.  


Happi said:


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


Will do.

Josh


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## JoshP12 (23 Dec 2020)

I am wrong!


			https://www.witpress.com/Secure/elibrary/papers/WS13/WS13002FU1.pdf
		


Assuming those rivers have plants in them .

That is some neat data. And it makes sense that we can limit everything low low and still grow! 

Jos


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## jaypeecee (19 Jan 2021)

Happi said:


> 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:






						Aquarium Plant Fertilizers - Sources of Nitrogen
					

Hi Everyone,  Ever since reading Diana Walstad's Ecology of the Planted Aquarium book on the topic of most plants preferring ammonium over nitrate, I have been digging deeper into this. And, I have found some interesting stuff that I'd like to share. In particular, I have been drawn to the use...



					www.ukaps.org
				




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


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## Zeus. (19 Jan 2021)

jaypeecee said:


> 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


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## jaypeecee (19 Jan 2021)

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


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## Zeus. (19 Jan 2021)

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.


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## dw1305 (19 Jan 2021)

Hi all,


Zeus. said:


> 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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## glasscanvasart (19 Jan 2021)

dw1305 said:


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


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’.


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## jaypeecee (19 Jan 2021)

Zeus. said:


> Most of the commercial ferts contain very little Ca and Mg...


Hi @Zeus. 

According to _James' Planted Tank_, only _Seachem Flourish_ contains Ca and Mg, 0.14 and 0.11, respectively W/W%.

JPC


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## jaypeecee (19 Jan 2021)

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


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## dw1305 (20 Jan 2021)

Hi all,


glasscanvasart said:


> 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’.





Zeus. said:


> 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. (20 Jan 2021)

dw1305 said:


> 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)



and with our tap water have a High Ca:Mg ratio( mine in pic below- new feature of IFC calculator)



adding some extra Mg improves the chances of the 'next ion' being a Mg instead of Ca most the time


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## jaypeecee (20 Jan 2021)

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:






						Aquarium Water Electrolytes
					

Hi Folks,  Recently, I have been making good use of the UKAPS thread entitled Sodium And Plants. I would like to extend this beyond sodium and beyond plants. Hence this new thread. I have found it difficult obtaining information about freshwater aquarium electrolytes pertaining to all aquarium...



					www.ukaps.org
				




JPC


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## Mortis (13 Feb 2021)

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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## X3NiTH (13 Feb 2021)

Mortis said:


> Is there an alternative Ca salt I could use that mixes stably with MgSO4 ?



Only if the Ca content in the intended mixture is below the solubility threshold for CaSO4 precipitate to form.



Mortis said:


> Should I replace KNO3 in my macros with CaNO3 instead ?



Only if the resultant mix contains no Sulphates or Carbonates or as above below CaSO4 and CaCO3 solubility threshold, thus the salts need to be Chloride based. If you want Calcium reinforced Macro you will need to source the Chlorides for all the major Ions or change nothing else but dose just the CaNO3 from its own bottle.


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## Mortis (14 Feb 2021)

X3NiTH said:


> Only if the Ca content in the intended mixture is below the solubility threshold for CaSO4 precipitate to form.
> 
> 
> 
> Only if the resultant mix contains no Sulphates or Carbonates or as above below CaSO4 and CaCO3 solubility threshold, thus the salts need to be Chloride based. If you want Calcium reinforced Macro you will need to source the Chlorides for all the major Ions or change nothing else but dose just the CaNO3 from its own bottle.


So if I were to change my GH Booster to a more soluble mix of Ca and Mg then I would need to use CaCl2 and MgCl2 instead of MgSO4 ?


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## Zeus. (14 Feb 2021)

Mortis said:


> GH Booster to a more soluble mix of Ca and Mg then I would need to use CaCl2 and MgCl2 instead of MgSO4 ?



Or do your own DIY one

What parameters are you after ? I have been working on anew Remininerliser calculator which works/does ratios as well, it will be some time before its released but happy to run some scenarios/parameters thought for you.
It even does reminerlising solutions - if the salts solubilities permit it, Just need your target dKH dGH and Ca:Mg:K ratio tank/WC Volume, list of salts you have at present as a starting place will help too


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## X3NiTH (14 Feb 2021)

Mortis said:


> So if I were to change my GH Booster to a more soluble mix of Ca and Mg then I would need to use CaCl2 and MgCl2 instead of MgSO4 ?



Yes, If you want to store a premixed solution in a bottle that you use at every waterchange you need to be careful not to exceed the solubility rules for Calcium Precipitate formations because of the presence of Sulphate from Magnesium, if it’s all Chlorides then it would all remain in solution.

You can use a combination of all the Chlorides and Sulphates if you wished if you direct dose to the tank as bare salts after waterchange rather storing it in a bottle and risking precipitation (SaltyShrimp GH+ used for remineralising RO water for sensitive shrimp is a mix of the chlorides of Magnesium and Calcium), even storing combinative mixtures together ‘dry’ for ease of use can cause precipitation issues so care needs to be taken (dry Calcium Nitrate and Potassium Phosphate together in a bag is a no no).

I use mainly the Carbonates of Magnesium and Calcium for remineralising RO/DI, this requires special preparation to store in a bottle, (I’ve done dry with carbonates direct to the tank but it looks like it’s snowed for a week or so) but I also augment the remineralisation with Magnesium Chloride and Magnesium Sulphate at waterchange just so I can have Chlorides and Sulphates present because plants require them. I look at the water as Total Nutrition and not just a  carrier for elements where sulphate and chloride excess can be hallmarks for pollution (in the wild), plants may not care but some aquatic animal species might.

A balanced mixture ensures you have all the required elements present in the water column, hopefully at levels that are Synergistic and not Antagonistic.

Hopefully that makes sense!


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## Mortis (16 Feb 2021)

Hi, Thanks for the advice. I do use Salty shrimp GH+ and knew it was a mix of CaCl2 and MgCl2 because of its hygroscopic nature. Im quite familiar with CaCl2 as Ive been using it for years to make DIY moisture absorbers for the cupboards and stuff.
As such I have no particular target ppm, I just want to add SOME Ca and Mg for the benefit of the plants. Right now I just mix 6tsp CaSO4 + 6tsp MgSO4 in a 600ml bottle and  add 50ml of this after every water change to my 150L tank, so as such the solution isnt kept for too long. There is already some MgSO4 mixed with my macros.
I was just kind of trying to optimize my Ca dosing and check if there's a better way to do it.


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## ceg4048 (17 Feb 2021)

Happi said:


> 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


Hi, the answer is yes, complete guesswork, sadly.


Happi said:


> or is there a science behind it?


No. The science is relevant to terrestrial plants, not to aquatic plants.


Happi said:


> 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.


No. Firstly there are very few valid test kits and this would not be the method to determine the consumption. Even if it were possible, the consumption rate for different species would vary. Secondly, nutrient uptake rates would vary based on environmental factors such as temperature, CO2 availability, lighting and so forth.

Cheers,


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