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GH+KH RO Reminiralzation Product Help.
- Thread starter CJayT
- Start date
Just to clarify guys, this is a RO remineralisation mix I'm trying to determine, so I won't be adding any trace elements - they'll be added via separate EI dosing - so there shouldn't be any issues with chelates I assume?
OK, did I do this right:
Assuming I got the formula above correct for the Calcium Chloride Hexahydrate that Darrel recommended, that's 17.28% Ca. So based on Darrel's calculations the Calcium Sulphate yields 23.3% Ca, that's a ratio of 1.348 - so to directly substitute 6.0g Calcium Sulphate in the James RO mix, I replace with 6.0 x 1.348 = 8.09g of Calcium Chloride ( CaCl2.6H20 ).
For the James mix, with the 1.2g of Calcium Chloride that is already included, that gives 9.29g in total of Calcium Chloride ( CaCl2.6H20 ) for the 75 litre water change.
That will mean adding 9.29g x 30.57% / 75 litres x 1000 = 37.9ppm of Chloride. Given my tap water has 61ppm Chloride per the Severen Trent water report, I assume that's not an issue at all?
For the James mix, with the 1.2g of Calcium Chloride that is already included, that gives 9.29g in total of Calcium Chloride ( CaCl2.6H20 ) for the 75 litre water change.
That will mean adding 9.29g x 30.57% / 75 litres x 1000 = 37.9ppm of Chloride. Given my tap water has 61ppm Chloride per the Severen Trent water report, I assume that's not an issue at all?
Hi all,
I think it should be: CaCl2.6H2O = 1 * Ca, 2 * Cl, 12 * H, 6* O so 40 + 71 + 12 + 96 = 219
RMM = 219 and 40/219 = 18.3% calcium
cheers Darrel
Right idea, wrong answer, you got a bit carried away with the hydrogen atoms (H), and a lot less carried away with the oxygen.
I think it should be: CaCl2.6H2O = 1 * Ca, 2 * Cl, 12 * H, 6* O so 40 + 71 + 12 + 96 = 219
RMM = 219 and 40/219 = 18.3% calcium
23.3/18.3 = 1.22 and 6 x 1.22 = 7.33g of CaCl.6H2O.
No, I don't do think so.
cheers Darrel
X3NiTH
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That level of Chloride shouldn’t be a problem, I used SaltyShrimp GH+ very successfully to remineralise before I went DIY and that’s made entirely of Magnesium Chloride and Calcium Chloride, at a GH of 6 and 150-200ppm TDS the Chloride is in excess of 100ppm.
As I said you’ve got to be careful with that calculator when translating formulas for it to calculate as Darrel pointed out that it’s easy to miss a few atoms. I should have been more careful when I posted the above solving, it was more a demonstration than the direct calculation.
🙂
As I said you’ve got to be careful with that calculator when translating formulas for it to calculate as Darrel pointed out that it’s easy to miss a few atoms. I should have been more careful when I posted the above solving, it was more a demonstration than the direct calculation.
🙂
Thanks Darrel - this is a veritable minefield!
So a mix for a 75 litre water change with RO water is:
7.73g Calcium Chloride
6.0g Magnesium Sulphate
75 litres RO Water
(+ Citric acid to 2-3Ph)
This will yield (according to James Planted Tank) 5 dGH. If I want to target 6 dGH, i need:
9.28g Calcium Chloride (CaCl.6H2O)
7.2g Magnesium Sulphate (MgSO4)
75 litres RO Water
(+ Citric acid to 2-3Ph)
That should give me Ca:Mg 3:1, and 6dGH?
For the dKH additive, I just mix 5.4g Potassium Carbonate (KHCO3) to the 75 litre RO mixture for 2 dKH?
. . . I think I'm going to need a lie down! lol
Thanks @X3NiTH - that good to read - I was going to use Salty Shrimp initially, and wondered exactly what was in it.
Don't worry on the calculator - its actually a very good tool, but clearly still a bit above my pay grade.
Hi all,
If I'm working it out for some-one else I usually check via "Rotala butterfly". I can remember the atomic weights of most of the common elements, and I'm not too bothered about precision, so usually if it is just for me I use a bit of mental "guesstimation".
It is useful to know the valency of the elements. Because calcium has a valency of two (Ca++ as an ion) you need to add two chlorine atoms (Cl- as an ion) to balance the equation and that gives you Ca(Cl)2.
cheers Darrel
The main issue is usually the <"water of crystallization">, it can make a lot of difference to the RMM and percentage of the nutrients.
If I'm working it out for some-one else I usually check via "Rotala butterfly". I can remember the atomic weights of most of the common elements, and I'm not too bothered about precision, so usually if it is just for me I use a bit of mental "guesstimation".
It is useful to know the valency of the elements. Because calcium has a valency of two (Ca++ as an ion) you need to add two chlorine atoms (Cl- as an ion) to balance the equation and that gives you Ca(Cl)2.
cheers Darrel
I am making a concentrate to auto-dose into a mixing container for automated water changes.
The Citric acid was discussed above - check post #31 onwards regarding preventing precipitation.
X3NiTH
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I know your trying to make a concentrate but you’ve swapped out using CaSO4 for CaCl alongside MgSO4 and so long as the concentrate is below the solubility threshold for CaSO4 precipitation then it will all stay in solution without the need to acidify.
I started preparing to going down the liquid concentrate remineralisation strategy last year but I got distracted by setting up a marine system which has its own set of challenges related to similar issues when it comes to DIY where a two part brine mixture has the most stability (the concentrate holding the MgSO4 is at the threshold for solubility and the mixture I found needs warmed to 30c to get it all into solution, ATI Absolute Ocean).
The reason I prepared to go liquid remineralisation was because of reactivity between salts.
Part A is usually unreactive though I have seen occasional off white discolouration in the powder here and there but it fully goes into solution for 25L (with help).
Part B is where the problems arose.
As you can see it’s turned into an amorphous crystal mass which is insoluble in water, it happened because CaNO3 and MgNO3 are exceptionally hygroscopic and probably absorbed any water vapour in the bag then melting with the phosphate forming an Apatite.
Not quite got round to planning the solution to partB yet but I’ll be putting the Nitrates, Sulphates and Chlorides in one concentrate and keeping the Phosphate separate (probably add it to my liquid bio carbon dose).
My recipe above was to simulate Karst water.
🙂
I started preparing to going down the liquid concentrate remineralisation strategy last year but I got distracted by setting up a marine system which has its own set of challenges related to similar issues when it comes to DIY where a two part brine mixture has the most stability (the concentrate holding the MgSO4 is at the threshold for solubility and the mixture I found needs warmed to 30c to get it all into solution, ATI Absolute Ocean).
The reason I prepared to go liquid remineralisation was because of reactivity between salts.
Part A is usually unreactive though I have seen occasional off white discolouration in the powder here and there but it fully goes into solution for 25L (with help).
Part B is where the problems arose.
As you can see it’s turned into an amorphous crystal mass which is insoluble in water, it happened because CaNO3 and MgNO3 are exceptionally hygroscopic and probably absorbed any water vapour in the bag then melting with the phosphate forming an Apatite.
Not quite got round to planning the solution to partB yet but I’ll be putting the Nitrates, Sulphates and Chlorides in one concentrate and keeping the Phosphate separate (probably add it to my liquid bio carbon dose).
My recipe above was to simulate Karst water.
🙂
Thanks. So as far as I can tell from Google the solubility threshold of Calcium Chloride Hexahydrate is 49.4g/100ml, and for MgSO4 is 36g/100ml.
Given I’m looking to dose 9.3g and 7.2g respectively per water change, if I aim to dissolve those in, let’s say, a 50ml solution with RO water per dose. Do you think I won’t need to add Citric acid to prevent precipitation?
So I could store a 5 litre mix with 930g of CaCl and 720g of MgSO4 (so enough for 100
days worth of doses @50ml each) without any precipitation issues?
Would you recommend adding potassium sorbate to that to act as a preservative?
I'm nearly sure CaCl in reaction with citric acid will form HCl and calcium citrate, which could precipitate due to low solubility. But I'm not a chemist, so maybe someone else could shed more light on this.
Last edited:
X3NiTH
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No the Solubility of CaSO4 is 0.2g/100ml, it’s likely at those ratios in a concentrate that you’ll end up with a MgCl ion solution and CaSO4 precipitation regardless of acidification (I think from what I have read is that you only get a 12% increase in solubility @pH 2.5) Just keep Calcium compounds (Chlorides/Nitrates) away from Sulphate compounds in concentrated solutions.
🙂
X3NiTH
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X3NiTH
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Just to point out that I did say above in post #54 that I would mix CaNO3 with MgSO4 as a concentrate, the maximum precipitation at these ratios in a solution at concentration above the saturation point for CaSO4 solubility would be the loss of less than 1 ppm of Calcium due to only having 1ppm of SO4 in the recipe, it’s an acceptable loss and the precipitate is easily filtered out if necessary.
🙂
🙂
Thanks, so it isn’t workable then even with Calcium Chloride then! If we have to adjust to solubility thresholds for CaSO4 it means dosing litres at a time, which isn’t practical - I feel like I’m going around in circles
I note your point above in using CaNO3, but it’s hard to get hold of and using it appears to add too much nitrate (>50ppm).
Ok so one last ditch attempt before I give all this up as a bad job - I can only see two possible options:
a) keep CaCl and MgSO4 concentrated solutions in separate containers. Problem is insufficient dosing heads available on my doser, so can either of those solutions have the Potassium Bicarbonate (KHCO3) added for the KH adjustment so that doesn’t have to be separate also?
Or
b) switch MgSO4 for MgCl (Magnesium Chloride), but then I’m adding no Sulphate other than via the MgSO4 in the macro dose every other day, and pushing the chloride levels higher (though that might not be an issue)?
