# Remineralizing question



## Hanuman (21 Feb 2022)

I am using RO. I have been remineralizing my tank for the past year (Ca:Mg / 3:1 / 20ppm:6.67ppm) with CaSO4 and MgSO4  not really considering the amount of sulfate being added, but considering I have had most my Panda Garra die one after the other for the past weeks I am looking for answers. I don't think this is the reason but I am taking the opportunity to improve things. So the question is: what would be preferable:

1. Magnesium sulphate + Calcium chloride




total ~92ppm of Cl+SO4
or
2. Magnesium chloride + Calcium sulfate?



total ~83ppm of Cl+SO4
or
3. Magnesium sulphate + Calcium sulfate



total ~ of 121ppm of SO4

Instinct says *2. Magnesium chloride + Calcium sulfate* due to lower overall ppm value but I am no biologist hence my question.

I am also considering adding some Magnesium Carbonate (or even Calcium Carbonate which I have readily available although extremely insoluble and only useful for 0.5 degree) to slightly raise my KH by 0.5 or even 1 degree. Yesterday I measured the water and I had 1dKH. In fact I am thinking if this low Kh is not the reason why my Panda Garra have left to the other world. Now that I remember I changed my filter cartridges and RO membrane in January and wonder if that is not the reason for all this shenanigans.

In any case thanks for the input.


----------



## Hanuman (21 Feb 2022)

As a side note, I have been looking for Magnesium chloride and only seem to be able to find what they call "technical grade or "industrial grade" MgCl2. This is the certificate of analysis of a supplier:



Would this be acceptable for aquarium use?


----------



## medlight (21 Feb 2022)

Remineralizo con Caso4+CaCl+ MgSo4, la relación entre SO4 y Cl 3:1


----------



## Wookii (21 Feb 2022)

I use MgSO4 and CaCl2 - the latter dissolves very easily, and both salts are widely available (over here in the UK at least).

You could also consider Magnesium Nitrate and/or Calcium Nitrate if you can source it, and wanted to reduce the amounts of Cl and SO4.


----------



## Hanuman (21 Feb 2022)

Wookii said:


> You could also consider Magnesium Nitrate and/or Calcium Nitrate


I rather not touch the nitrate for now as that is being provided by my AIO fert which I still have plenty but something to consider later on. 

I have been trying to source Magnesium chloride but for some reason I can only source industrial grade and I don't feel that comfortable with that. Best bet would be Calcium chloride as that one I can find food grade.


----------



## dw1305 (21 Feb 2022)

Hi all,


Hanuman said:


> Would this be acceptable for aquarium use?


It would depend on which salt the other ~50%  was. It may just be the <"water of crystallization"> because I'm assuming that both CaCl2 and MgCl2  are the hexahydrate form, MgCl2.6H2O etc.


Hanuman said:


>





Hanuman said:


> *Magnesium chloride + Calcium sulfate* due to lower overall ppm value but I am no biologist hence my question.
> 
> I am also considering adding some Magnesium Carbonate (or even Calcium Carbonate





Wookii said:


> I use MgSO4 and CaCl2


I would just use "Epsom Salts" (magnesium sulphate heptahydrate (MgSO4.7H2O)) and ~10% Mg and <"a smidgen">* of calcium carbonate (CaCO3) to add Ca and dKH.  If you didn't want to add any dKH then CaCl2.6H2O is your go to chemical.

If you did use Mg(NO3)2.6H2O then adding 10 ppm (mg/l) Mg  would also add 51 ppm NO3 and you would have to take into account the water of crystallization, so the RMM would be  256 and 9.5% Mg and 48% NO3.

*Specially for @Hufsa 

cheers Darrel


----------



## Hanuman (21 Feb 2022)

dw1305 said:


> It would depend on which salt the other ~50% was. It may just be the <"water of crystallization"> because I'm assuming that both CaCl2 and MgCl2 are the hexahydrate form, MgCl2.6H2O etc.


Yes they are the hexahydrate forms. That's what I thought as well, mostly water. But since usually industrial grades are less refined there could be some lead or other nasty stuff in there to levels which are not disclosed. I was able to find CaCl2 food grade though so I guess I'll just forget about MgCl2.



dw1305 said:


> I would just use "Epsom Salts" (magnesium sulphate heptahydrate (MgSO4.7H2O) and ~10% Mg and smidgen of calcium carbonate (CaCO3) to add Ca and dKH.


That's what I did earlier this morning before leaving to work to slightly increase dKH. But I did a goal seek calculation and it shows me that the max dKH I can have before I reach the in-tank solubility limit of CaCO3, is 0.6 dKH (max 0.8 dKH if I increased solubility setting to 100% - which is not a good idea). If I wanted to increase dKH more than that I would need to use something else and that something else can only be Magnesium carbonate as I don't want to start adding other ions like Potassium, Nitrates or whatnot. That's why I considered Magnesium Carbonate as that is way more soluble.


----------



## dw1305 (21 Feb 2022)

Hi all, 


Hanuman said:


> But I did a goal seek calculation and it shows me that the max dKH I can have before I reach the in-tank solubility limit of CaCO3, is 0.6 dKH


Yes, technically CaCO3 is insoluble in water, but soluble in weak acids.  You can actually use this to your advantage, it gives you a negative feedback loop where the Ca++ and 2HCO3- ions only go into solution when the pH dips.  Plants don't have a huge calcium requirement, so it should fulfill that. 

If you have <"hard tap water you can use that"> or you can just add a bit of limestone to the tank.  I'm going to assume caged bird keeping is popular in Thailand, so shell grit should be available?

cheers Darrel


----------



## Wookii (21 Feb 2022)

Hanuman said:


> I did a goal seek calculation and it shows me that the max dKH I can have before I reach the in-tank solubility limit of CaCO3, is 0.6 dKH



You are injecting CO2 aren't you? In which case you'll dissolve much more CaCO3 and get a much higher dKH. In my last tank I had a load of Seiryu stone which had lots of CaCO3 in it, and despite doing water changes with pure un-mineralised RO, the tank maintained a pretty consistent KH of around 6, and a GH of 11-12, just from the dissolved CaCO3 from the rock and MgSO4 in the EI ferts.


----------



## Hanuman (21 Feb 2022)

dw1305 said:


> Yes, technically CaCO3 is insoluble in water, but soluble in weak acids


Indeed. I omitted that very essential part. Thank you.



dw1305 said:


> If you have <"hard tap water you can use that"> or you can just add a bit of limestone to the tank. I'm going to assume caged bird keeping is popular in Thailand, so shell grit should be available?


I use RO. Yes caged bird is popular in Asia in general. I think cuttlebone is also easily found considering all the squid they eat around here.



Wookii said:


> You are injecting CO2 aren't you? In which case you'll dissolve much more CaCO3 and get a much higher dKH


Yes. That meets what Darrel said above. The solubility of all those compound with have in the calculator are based on neutral water at 20 degrees.



Wookii said:


> In my last tank I had a load of Seiryu stone which had lots of CaCO3 in it, and despite doing water changes with pure un-mineralised RO, the tank maintained a pretty consistent KH of around 6, and a GH of 11-12, just from the dissolved CaCO3 from the rock and MgSO4 in the EI ferts.


Yes. I had considered having some stone initially. It could be same as adding some shell or cuttlebone. I might start with a small piece and increase progressively until I read desired dKH but that might take several weeks to have consistent readings.


----------



## Wookii (21 Feb 2022)

Hanuman said:


> Yes. I had considered having some stone initially. It could be same as adding some shell or cuttlebone. I might start with a small piece and increase progressively until I read desired dKH but that might take several weeks to have consistent readings.



Yeah, I wasn't suggesting you use stone to add CaCO3, the cuttlebone or oyster shell grit will be a better way to add it 'naturally' - more that you'll end up at a higher KH level than you expected from your calculations due to the carbonic acid.

I've always wanted to try and use the cuttlebone or oyster grit approach, but I think its going to be difficult to regulate in a CO2 injected tank, whereas adding KHCO3 or K2CO3 is easier to accurately control (though I appreciate that you don't want to add the extra potassium).


----------



## Hanuman (21 Feb 2022)

Wookii said:


> I've always wanted to try and use the cuttlebone or oyster grit approach, but I think its going to be difficult to regulate in a CO2 injected tank, whereas adding KHCO3 or K2CO3 is easier to accurately control (though I appreciate that you don't want to add the extra potassium).


Yes much easier considering you know exactly what you are adding. I might just stick to CaCO3. Reality is I don't need to increase dKH that much maybe 1 point up at most. I need to measure dKH at the end of the week before WC to see what the new reading is.


----------



## Wookii (21 Feb 2022)

Hanuman said:


> Yes much easier considering you know exactly what you are adding. I might just stick to CaCO3. Reality is I don't need to increase dKH that much maybe 1 point up at most. I need to measure dKH at the end of the week before WC to see what the new reading is.



If you are happy to dry dose, that's probably the best way forward for you. It doesn't work for me, as I automate everything with auto-dosers, and the CaCO3 is too insoluble to be able to use in a concentrated liquid.


----------



## X3NiTH (21 Feb 2022)

Here’s what I do for remineralisation with Calcium and Magnesium Carbonate, I previously posted here in another thread, it’s an attempt at simulating Karst waters.

_Add to 900ml Refrigerated Cold Carbonated RO/DI (one full level round in new type soda stream machine is enough)-

2g Calcium Carbonate
1g Magnesium Bicarbonate
0.25g Ascorbic Acid

In order to keep as much CO₂ from off gassing the above mixture is added to a food spice diffusion bag and placed fully and quickly into the neck of the briefly open bottle, above the cold pressurised water making sure to close the top tightly before shaking to mix (adding the powder without the bag can turn the water into a volcano, not quite bicarbonate into vinegar but it gets close). This mix goes back into the fridge for 24hrs just to give it time to go somewhat into solution, it's more of a suspension that can sediment but over 24hrs there is a massive reduction in sedimentation happening and the liquid takes on a cloudy lemonade look telling me some bicarbonate has formed, when the bottle is reagitated and the sedimentation goes back into suspension the resultant liquid looks like skimmed milk (importantly the mix has fully exited the spice bag by this time).

A day before performing the water change I will add to the 24.1L (or thereabouts water volume it may be more, I just need enough space in there to take the 900ml back and not spill over the lip when the Jerry can is sitting upright and level)-

1g Potassium Bicarbonate
0.75g Magnesium Nitrate
0.5g Magnesium Sulphate
0.2g Potassium Phosphate
Pinch of Magnesium Chloride

I don't measure the Magnesium Chloride out because it really is just a teeny tiny pinch just enough so Chloride is non-zero hence its magnesium content I don't add to the final numbers I'll give below.

Once these salts are in the water in the Jerry can I then take the cold bottle of bicarbonate/carbonate solution from the fridge and add it all in (opening the bottle slowly and no vigorous agitation beforehand as to not off gas too much CO₂), fish out the empty spice bag floating at the top and pour half the liquid into the Jerry can, the remaing liquid in the bottle is given a swirl around to pick up any sedimentation and poured directly into the Jerry can, I then seal the top and leave it overnight to go clear.

24hr dwell time for everything in the water is not any special number it's just the minimum time I have so far left it to sit before use and since I do two jerry cans at a time. The other end of the wait spectrum is a Jerry can sitting 2 weeks before use with CO₂ still being retained at 30-35ppm.

The resultant values in mg/L are (resultant water TDS <150) -

Ca / 32
Mg / 14.42 (not counting MgCl addition)
K / 17.9
NO₃ / 15
PO₄ / 5.58
S / 2.6
Cl / Non zero

GH / 7.8 (MgCl addition probably pushes this to nearer 8)
KH / 7.8
pH / 7.8 (@ atmospheric CO₂ from stored sample which correlates with in tank behaviour)

In tank CO₂ injection phase behaviour -
pH / 6.2 (estimated 30ppm CO₂ via Lime Green colour change to Drop Checker 4dKH sample)_

The recipe is easily adapted, I have tried dosing the carbonates of Calcium  and Magnesium dry into a CO2 injected tank and it took a week or so of injection phases for the Calcium to fully dissolve and not look like a fine dusting of snow on the substrate.

I did end up here from using Cuttlefish Bone for remineralisation but wanted something quicker so I turned the Cuttlefish bone into dust and dosed that and it worked a lot faster (finer the powder the greater the surface area to volume), hands stank of fish for a bit afterwards and opted to skip that step and source the pure carbonates instead.


----------



## Happi (21 Feb 2022)

@Hanuman

I believe the So4 numbers are incorrect in the first post.

Target:
Ca     20
Mg    6.67

1. Magnesium sulphate + Calcium chloride
Cl    35.38
So4    26.4

2. Magnesium chloride + Calcium sulfate
Cl    19.46
So4    48

3. Magnesium sulphate + Calcium sulfate
So4    74.4


----------



## Happi (21 Feb 2022)

you can also add some Ca and Mg Gluconate to your mix, this is good food source for bacteria as well, if your aquarium condition are right this will also help to reduce the NO3 if you were to use Ca and Mg Gluconate.


----------



## Hanuman (22 Feb 2022)

X3NiTH said:


> Here’s what I do for remineralisation with Calcium and Magnesium Carbonate, I previously posted here in another thread, it’s an attempt at simulating Karst waters.
> 
> _Add to 900ml Refrigerated Cold Carbonated RO/DI (one full level round in new type soda stream machine is enough)-
> 
> ...


This requires some serious skills far above and beyond my pay grade 😅.


----------



## Hanuman (22 Feb 2022)

Happi said:


> I believe the So4 numbers are incorrect in the first post.
> 
> Target:
> Ca     20
> ...


Nope. Figures are correct. On the other hand you used values relating to the anhydrous states of those salts (CaSO4 and MgSO4) which gives you the values you found. In general it is far more common to find the hydrate versions, for instance CaSO4·2H2O (Calcium sulfate *dihydrate*) and MgSO4‧7H2O (Magnesium sulfate *heptahydrate*).


----------



## Happi (22 Feb 2022)

Hanuman said:


> Nope. Figures are correct. On the other hand you used values relating to the anhydrous states of those salts (CaSO4 and MgSO4) which gives you the values you found. In general it is far more common to find the hydrate versions, for instance CaSO4·2H2O (Calcium sulfate *dihydrate*) and MgSO4‧7H2O (Magnesium sulfate *heptahydrate*).


Just to be clear which one did you use in your first post?


----------



## Hanuman (22 Feb 2022)

The hydrate forms. CaSO4·2H2O and MgSO4‧7H2O which is what I use.


----------



## Happi (22 Feb 2022)

Hanuman said:


> The hydrate forms. CaSO4·2H2O and MgSO4‧7H2O which is what I use.
> View attachment 183197


Either am loosing my mind today or something still isn't adding up. I get the following:


----------



## Hanuman (22 Feb 2022)

Interesting. I will check the backend of the calculator today see if there is an issue.


----------



## Hanuman (22 Feb 2022)

I think I figured it out. The calculator was adding up the extra oxygen from the hydrate (7H2O - 11 atoms of O instead of only 4) to SO4 when a hydrate was selected which should not happen. No matter the hydrate, SO4 and Ca should remain constant. Only the required mass changes. This will require an immediate update and release as I view this as an important fix. I will discuss with @Zeus.  first so that we are on the same page.
@Happi Thanks for pointing this out.


----------



## Happi (22 Feb 2022)

Hanuman said:


> I think I figured it out. The calculator was adding up the extra oxygen from the hydrate (7H2O - 11 atoms of O instead of only 4) to SO4 when a hydrate was selected which should not happen. No matter the hydrate, SO4 and Ca should remain constant. Only the required mass changes. This will require and immediate update and release as I view this as an important fix. I will discuss with @zeus first so that we are on the same page.
> @Happi Thanks for pointing this out.


Make sense, I thought I was going crazy 🤪 today.


----------



## Hanuman (23 Feb 2022)

If I had to chose between Chloride and Sulfate which one would be the better one?


----------



## dw1305 (23 Feb 2022)

Hi all,


Hanuman said:


> If I had to chose between Chloride and Sulfate which one would be the better one?


Plants don't have much requirement for either sulphur (S) or chlorine (Cl), so ideally you would want to add as little a you can compared to the metal ion that you do want e.g. potassium (K), magnesium (Mg) etc.

All of chloride containing salts, that we might be interested in, <"are soluble">, which would be an advantage. The disadvantage is that chloride (Cl-) is  monovalent, meaning that you need two of them when you add a divalent cation, so calcium chloride is CaCl2.nH2O etc.

Sulphates are a mixed  bag in terms of solubility, but again it is only calcium sulphate  (CaSO4.nH2O), that is both of interest to us and although not actually insoluble is "sparingly soluble".

For divalent cations sulphates are probably best, so magnesium sulphate (MgSO4.nH2O) rather than magnesium chloride (MgCl2).

The advantage of nitrate (potassium nitrate (KNO3 etc.)) and phosphate compounds (dipotassium phosphate (K2PO4) etc) would be both cation and anion are plant nutrients.

cheers Darrel


----------



## Hanuman (24 Feb 2022)

Thank you Darrel. The question was more to know if there was one worse than the other (for flora and fauna) in terms of concentration and if I had to prioritize one over the other, which one would it be.

I came up to the following theoretical remineralization strategy. I slightly changed my Ca:Mg ratio to 20:8 to bump up slightly dGH but also to have less comas in those numbers! I could go higher but don't think it's necessary. All shrimps have been doing just fine for the past year with that hardness. I think I better stay with MgSo4 + CaSo4. I could of course add some CaCl2 to further reduce sulfate but then I would have to deal with Cl and I am not sure of the benefits of this. There is probably already some Cl in the fertilizer I am using.

I want to add some MgCo3 to increase dKH as by week end I noticed the dKH is now close to 0. Alternatively I could also use CaCo3 which has the advantage of reducing overall PPM value by reducing SO4 PPM value. All this might sound a bit too simplistic to all you chemist cowboys but keep in mind I am trying to make this as simple as possible without the need to making complicated mixes while making things work.

1. Is there any drawback to this strategy and if I had to choose between MgCO3 and CaCo3, which one would be preferable?









2. I don't have the space to store large amounts of water and I normally throw in the MgSO4 and CaSo4 in the tank (in the skimmer - nice snow effect) straight after water change . This is usually not the standard polite procedure to remineralize water but since it's only dGH I figured it's not a big of a deal, at least I haven't seen any ill effect so far. However since I would now be adding carbonates to the water via MgCo3 or CaCo3, adding those directly to the tank would probably be a very bad (impolite, even deadly) idea due to PH possibly spiking. I know most people prepare they remineralized water and let it sit for a day or so. No can do. What are my options here?

Thank you gentlemen and gentlewomen.


----------



## dw1305 (24 Feb 2022)

Hi all, 


Hanuman said:


> The question was more to know if there was one worse than the other (for flora and fauna) in terms of concentration and if I had to prioritize one over the other, which one would it be.


I'm not sure there is a huge amount of difference, they would both be <"common anions"> in nearly all freshwater.  Sulphate ions (SO4--) will contribute slightly more to the conductivity than chloride (Cl-) ions, purely because <"they have more charge">.


Hanuman said:


> I slightly changed my Ca:Mg ratio to 20:8 to bump up slightly dGH ....... I could go higher but don't think it's necessary. All shrimps have been doing just fine for the past year with that hardness. I think I better stay with MgSo4 + CaSo4.


I would just carry on, I think "_shrimps have been doing just fine" _is probably the only relevant bit.


Hanuman said:


> Is there any drawback to this strategy and if I had to choose between MgCO3 and CaCo3, which one would be preferable?


I think in practical terms there isn't any difference, CaCO3 is cheaper and easier to find, but neither is very soluble.


Hanuman said:


> However since I would now be adding carbonates to the water via MgCo3 or CaCo3, adding those directly to the tank would probably be a very bad (impolite, even deadly) idea due to PH possibly spiking.


The pH won't spike, it will just go to pH8 fairly slowly, calcium and magnesium carbonates are "weak bases". If you added a <"strong base"> (like sodium hydroxide (NaOH)) you would get a pH spike, potentially to pH11, because the NaOH would disassociate fully (and pretty much instantly) to Na+ and OH- ions. 

cheers Darrel


----------



## Hanuman (24 Feb 2022)

Thank you sir. As always, excellent.


dw1305 said:


> I think in practical terms there isn't any difference, CaCO3 is cheaper and easier to find, but neither is very soluble.


MgCO3 is ~10 times more soluble than CaCO3, but yes comparatively to all compounds we have added they are highly insoluble.



dw1305 said:


> The pH won't spike, it will just go to pH8 fairly slowly, calcium and magnesium carbonates are "weak bases". If you added a <"strong base"> (like sodium hydroxide (NaOH)) you would get a pH spike, potentially to pH11, because the NaOH would disassociate fully (and pretty much instantly) to Na+ and OH- ions.


Very good news. Would there be a better time to add MgCO3? Say before CO2 is on, during or after, or it wouldn't matter?


----------



## dw1305 (24 Feb 2022)

Hi all, 


Hanuman said:


> MgCO3 is ~10 times more soluble than CaCO3


It is, but still less than 1/4 gram in a litre. Where this is relevant if you add both of them, Ca++ ions will <"come out of solution first"> (as CaCO3), before any MgCO3 forms, due to the <"common ion effect">. 


Hanuman said:


> Say before CO2 is on, during or after, or it wouldn't matter?


When the CO2 was on would give you quicker dissolution, because you would have changed the  <"CO2 ~  HCO3- ~ pH equilibrium point">. When the CO2 went off any "extra" of carbonate would <"come back out of solution"> as the <"least soluble"> carbonate salt, so realistically always as CaCO3.  

cheers Darrel


----------



## Ria95 (24 Feb 2022)

You will get the best dissolution  of CaCO3 when the water is most acidic, this usually means end of the day after CO2 injection. The faster you dissolve that CaCO3 the  faster the  pH spikes as the extra CO3 (2-) will bind with the available H+ and shift the equilibrium to the right.

As our aquariums are essentially  open  air(CO2)- CaCO3- H2O systems, in small amounts CO3 will eventually end up as HCO3 (distribution of carbonate species in relation to  ph), reason why I sugest adding bicarbonates directly and avoid the entire pH spike and dissolution issues.


----------



## Hanuman (24 Feb 2022)

Ria95 said:


> reason why I sugest adding bicarbonates directly and avoid the entire pH spike and dissolution issues.


Not sure I understood this.


----------



## Ria95 (24 Feb 2022)

Adding bicarbonates directly will not increase the pH as much or as abruptly and are readily soluble compared to CaCO3 . As you don't want to have a high pH and will ultimately end up with HCO3 in both cases, it makes sense to use bicarbonates from the start.


----------



## Hanuman (24 Feb 2022)

Ok but which bicarbonate? I only have MgCO3 and CaCO3 available. I cannot afford adding potassium bicarbonate as I am already providing enough K through fertilizers.


----------



## dw1305 (24 Feb 2022)

Hi all,


Hanuman said:


> Ok but which bicarbonate? ...adding potassium bicarbonate as I am already providing enough K through fertilizers.


You only really have the option of potassium or sodium bicarbonate (KHCO3 / NaHCO3). It is only group 1. alkali metals that form soluble carbonates. 

cheers Darrel


----------



## X3NiTH (26 Feb 2022)

The reason I use pressurised CO2 into low temperature water via a Sodastream is to form as much Calcium Bicarbonate and Magnesium Bicarbonate as possible to aid in quick dissolution while adding extra Ascorbic acid helps further. The process really isn’t difficult or that technical it’s just a little bit labor intensive but it is better than adding a teaspoon of something you are wanting to limit. 

If you really want complete control over exacting mineralisation then you have to get a little creative. You don’t have to use Sodastream, a Soda Bottle that uses the small disposable one time use cartridges would be sufficient.


----------



## Hanuman (27 Feb 2022)

X3NiTH said:


> The process really isn’t difficult or that technical it’s just a little bit labor intensive


Well it does require one to understand the chemical reactions. Personally I wouldn't dare go through that procedure as I am pretty certain I would screw things over. If you ever come to Thailand, let me know and I'll open my kitchen for a demonstration 🙂


----------

