# Seiryu stone CACO3 solubility



## FishWorks (1 Jul 2021)

Hey All,

I recently setup a tank with Seiryu stone and I have read that it affects PH, KH and GH when your PH is below 7.
Is this true?

It kinda makes sense to me because PH below 7 is acid which dissolves the calcium carbonate.
Vice versa for PH above 7, its alkaline water, so shouldnt dissolve the CACO3.

My water parameters are 8.1 before CO2 and 7.1 after CO2. So I shouldnt expect fluctuations in PH, KH or GH right?

Thanks


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## Wookii (1 Jul 2021)

It depends to a certain extent how hard or soft your water is to start with - if it very hard to start with, and already contains a lot of dissolved Calcium Carbonate then you may reach the solubility limit and no more CaCO3 will dissolve. That is possibly the rarer case though.

More typically though, if your water is not quite that hard to start with, CO2 injection will result in CaCO3 being dissolved from the Seiryu stone. I'm not sure on whether the absolute pH being below 7.0 is a factor or not, as CO2 injected into the water column results in the creation of carbonic acid regardless of the absolute pH - @X3NiTH or @dw1305 might be able to confirm that - but certainly at a pH below 7.0 you will know for sure that there are sufficient acids in the water to start dissolving the Calcium Carbonate.

Anyone wanting to maintain a soft water tank should try and avoid using Seiryu stone (or any other stone containing CaCO3), or using very minimal amounts of it. I used a lot of Seiryu stone in my last tank where I was aiming for soft water parameters using RO water (CO2 injected) - in the end so much CaCO3 was being dissolved from the stone that even using pure RO for daily 25% water changes, without _any_ remineralisation beyond some MgSO4 in the macro fertilizer mix, the tank self maintained a KH around 6-7 and a GH around 11-12.


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## Zeus. (1 Jul 2021)

Solubility varies with pH like @Wookii said.

I did a mod to the IFC Fert Calculator so for a given pH it would give the solubility limit of CaCO3 so it could be dosed each week and save your stone, it hasn't been finished and it is subjective to getting the right pH in the first place.
But any stone CaCO3 with in it does the same, if unsure just put a drop of a weak acid on the stone and see if it bubbles- if it bubbles it has CaCO3 in it


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## Krisps21 (1 Jul 2021)

I have used it before. My pH is is 6.5 (5.2 with co2) kh 1 and gh 3. When I used it my gh went up to gh 12 😬 and my kh went up to 4. I've never used it again since


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## FishWorks (1 Jul 2021)

Zeus. said:


> View attachment 171394
> 
> Solubility varies with pH like @Wookii said.
> 
> ...



Zeus,

I think this helps...
This graph you just posted presents solubility limits for CaCO3 at different PH Levels right?
With the way your graph appears and my lowest PH of 7.1 after CO2, it looks like CaCO3 solubility in my aquarium should be between 0.01mg/l and 0.001mg/l, which is pretty much 0mg/l.
Although I'm not sure how this contributes to how much CaCo3 is dissolved over longer time periods, maybe changes in days or weeks.


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## Wookii (1 Jul 2021)

Is the Y-axis on that graph definitely correct, or should if be 'grams per litre'?

I have to admit to not quite fully understanding the chemistry, but 1dKH is supposed to be 17.86mg/L of CaCO3, so how do we get to, say 6dKH, which would be 107.16mg/L if only 0.01-0.001mg/L dissolves at pH8.0?


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## FishWorks (1 Jul 2021)

Wookii said:


> Is the Y-axis on that graph definitely correct, or should if be 'grams per litre'?
> 
> I have to admit to not quite fully understanding the chemistry, but 1dKH is supposed to be 17.86mg/L of CaCO3, so how do we get to, say 6dKH, which would be 107.16mg/L if only 0.01-0.001mg/L dissolves at pH8.0?


You wont arrive at 6dKH at that rate of change.
The dissolving of CaCO3 is there, but its so slow, that there is barely any change at PH 8. 
Perhaps anything above 7PH will have insignificant increase in CaCO3 levels?
Why would the Seiryu stone dissolve if the water is alkaline? like mine at 7.1PH.

A bunch of sites are telling me just to perform the 50% weekly water change.
However, I really want to understand if CaCO3 needs to be in acidic solution to dissolve.


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## Tim Harrison (1 Jul 2021)

It's not the least bit important, especially compared to optimising your CO2 flow and distribution. But maybe this will help...






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## FishWorks (2 Jul 2021)

Tim Harrison said:


> It's not the least bit important, especially compared to optimising your CO2 flow and distribution. But maybe this will help...
> 
> 
> 
> ...


Thanks, now i'm confident I wont get parameter swings from this rock.


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