# Calcium & Magnesium ppm's for RCS (Neocaridina Davidi) ?



## MichaelJ (5 Jan 2022)

Hello, I am on a quest to tweak my water a bit (lowering TDS essentially) and I am just curious what Ca:Mg levels people are keeping their Cherry shrimps at? (long term and breeding successfully)   Currently I am aiming for 36 ppm of Ca and 9 ppm of Mg (~7 GH) and that works very well.  I am sure I could safely dial that down to 26:7 (Ca:Mg ppm's)  or so.... but would like to hear the ranges fellow shrimp _lovers_ are at?

Cheers,
Michael


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## erwin123 (5 Jan 2022)

I'm using straight tapwater which my water supply report says has 24ppm Ca and 1.6ppm Mg.  I add about 2ppm Mg weekly. However, I'm only breeding standard grade cherries mainly as the cleanup crew, not the high grade ones which might be more sensitive. That should translate to gH 6 which some internet sites say is good for Cherries?


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## Aqua360 (5 Jan 2022)

MichaelJ said:


> Hello, I am on a quest to tweak my water a bit (lowering TDS essentially) and I am just curious what Ca:Mg levels people are keeping their Cherry shrimps at? (long term and breeding successfully)   Currently I am aiming for 36 ppm of Ca and 9 ppm of Mg (~7 GH) and that works very well.  I am sure I could safely dial that down to 26:7 (Ca:Mg ppm's)  or so.... but would like to hear the ranges fellow shrimp _lovers_ are at?
> 
> Cheers,
> Michael



In terms of your TDS, are you going to use RO and remineralise with a branded shrimp salt? As that would likely take away a lot of guesswork


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## Zeus. (5 Jan 2022)

The Ca: Mg ratios vary quite a bit with commercial products




and some products the data is unknown



But a Ca:Mg ratio of 3.0 : 1.0 is what many aim for
If you water supply has stable Ca and Mg levels I can work out what you need to add to get to your targets, or take the RO water route.


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## MichaelJ (5 Jan 2022)

Aqua360 said:


> In terms of your TDS, are you going to use RO and remineralise with a branded shrimp salt? As that would likely take away a lot of guesswork


Hi @Aqua360, @Zeus. Thanks. I should have mentioned that am I already using RO water and doing my own salts etc. so I am already in full control over the water parameters. I am just curious what people are aiming for with Ca and Mg ppm's to figure how low I can safely go with my Ca:Mg dosing without interfering with molting/exoskeleton development.  


erwin123 said:


> I'm using straight tapwater which my water supply report says has 24ppm Ca and 1.6ppm Mg. I add about 2ppm Mg weekly. However, I'm only breeding standard grade cherries mainly as the cleanup crew, not the high grade ones which might be more sensitive. That should translate to gH 6 which some internet sites say is good for Cherries?


Hi @erwin123, Thanks for the reply. Ca 24-25 ppm seems to be a number I encounter quite frequently as well. In a 1:~3 ratio.

Cheers,
Michael


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## MichaelJ (6 Jan 2022)

Anyone else have a say on the Ca contents?  @Wookii, your a shrimp keeper I believe?

Cheers,
Michael


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## Wookii (6 Jan 2022)

MichaelJ said:


> Anyone else have a say on the Ca contents?  @Wookii, your a shrimp keeper I believe?
> 
> Cheers,
> Michael



Hey Michael, the more the better for cherry shrimp. The minimum would be a GH of around 5-6, in a 3:1 Ca:Mg ratio, but more is better for them. Your current water parameters should be fine in terms of GH.

Are you seeing anything that has you concerned currently? Moulting issues or lack of new shrimplets?


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## MichaelJ (6 Jan 2022)

Wookii said:


> Hey Michael, the more the better for cherry shrimp. The minimum would be a GH of around 5-6, in a 3:1 Ca:Mg ratio, but more is better for them. Your current water parameters should be fine in terms of GH.
> 
> Are you seeing anything that has you concerned currently? Moulting issues or lack of new shrimplets?


Hi @Wookii Thanks for the feedback! No issues at all that I am aware of - happy adults and plenty of shrimplets, but I am on a quest to lower my overall TDS in the tank where keep shrimps, so I am trying to tweak wherever I can - I am currently hovering in the TDS 210-230 ppm range - which is OK for my Cheeries and Tetras in that tank, but getting it down a bit might be beneficial, especially if I want to introduce Crystal Reds. I am probably just going to do a very minor tweak to the Ca and Mg contents, but cut back on my _very_ generous NPK dosing as an experiment. 

Cheers,
Michael


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## Wookii (6 Jan 2022)

What is your other dosing? What do you add for KH if anything?

I dose EI levels of ferts, including a double dose of KNO3 as my surface plants suck up so much of it, I use RO and remineralise to KH~1-1.5 and GH around 5-6, TDS is consistently around 160ppm.


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## MichaelJ (7 Jan 2022)

Wookii said:


> What is your other dosing? What do you add for KH if anything?



Hi @Wookii ,

This is my current dosing for my WC water (I front load everything for the week):

CaSO4.2H2O to target 36ppm of Ca.
MgSO4 to target 5 ppm of Mg
Mg(NO3)2.6H2O to target 20 ppm of NO3 (adds 4.5 ppm of N and 4 ppm of Mg)
and finally KH2PO4 to target 9.2 ppm of PO4 (adds 3 ppm of P and 3.8 ppm of K)  - see below vs. K
Of course with the SO4 compounds come a lot of Sulphate.

I blend 20% tap with my Tap/RO WC water to target 2-2.5 KH (CO3). My Tap water is special as it comes out at zero GH... stripped from Ca and Mg due to our KCL resin based water softener - hence my tap water is heavily loaded with Potassium (K) from the ion exchange (and unknown quantities of Chloride) - likely in the 150-180ppm range, so the 20% mix gives me around 35ppm of K + what I get from the KH2PO4 above.

All in all the, math totally adds up to about 220 ppm (the 20% tap contributes about 80ppm, the RO is about 10ppm and the salts above contributes about 120ppm), so depending on how cavalier I am with my measurements of the salts I usually end up with somewhere around 210-230 ppm.  (In addition, I add a few ppms of traces throughout the week - which is insignificant in the grand scheme of things). 

This is the dosing I am planning:

CaSO4.2H2O to target 30ppm of Ca.
MgSO4 to target 6 ppm of Mg
Mg(NO3)2.6H2O to target 10 ppm of NO3 (adds 2 ppm of Mg)
and finally KH2PO4 to target 4 ppm of PO4 
(About 6.2 GH from the Ca and Mg).

Instead of 20% tap I will reduce it to 10% which would get me around 1-1.5 KH and 20 ppm of K. 

This whole exercise should, if am doing the math correctly, reduce the TDS of my WC water to about ~140ppm.  (10 ppm from RO, 40 ppm from tap and 90 ppm from the salts).

Cheers,
Michael


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## Wookii (7 Jan 2022)

Sounds like a reasonable plan. Is this a CO2 injected tank? If so, a KH of 1-1.5 is plenty to add a little buffering, if not, KH isn’t particularly necessary 

If it is a CO2 injected tank, be careful on reducing your NO3 too far, particularly if you have floating plants - as I say, I have to double dose KNO3 as I found a standard EI dose gets completely stripped out during a week with the floaters. I know you have a lot of K in your tap water (is that from a softener?), but you could use KNO3 which will boost your K back up a bit - never a bad thing.

It makes sense reducing your PO4 dosing too, I know you’ve got to that point to reduce GSA but really 3ppm should be plenty for that purpose.


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## MichaelJ (7 Jan 2022)

Wookii said:


> Sounds like a reasonable plan. Is this a CO2 injected tank? If so, a KH of 1-1.5 is plenty to add a little buffering, if not, KH isn’t particularly necessary


Hi @Wookii,  Thanks.  No, both my tanks are low-energy. Very densely planted though. I do like the idea of having a little bit of buffering capacity nevertheless.  


Wookii said:


> If it is a CO2 injected tank, be careful on reducing your NO3 too far, particularly if you have floating plants - as I say, I have to double dose KNO3 as I found a standard EI dose gets completely stripped out during a week with the floaters.


I do have a lot of floating plants (Frogbit, pennywort and duckweed).  I may have to set my NO3 target a bit higher than 10ppm. 



Wookii said:


> I know you have a lot of K in your tap water (is that from a softener?), but you could use KNO3 which will boost your K back up a bit - never a bad thing.


Yes, the K is from the softener. The water out of the softener probably contains somewhere around 150-180ppm of K - but I do not know exact amount. 

Now that I think about it, If I would go 100% RO, instead of adding that 10% tap I could just as easily use K2CO3 to raise my KH to ~1.5 and that would give me a predictable 25ppm K.  



Wookii said:


> It makes sense reducing your PO4 dosing too, I know you’ve got to that point to reduce GSA but really 3ppm should be plenty for that purpose.


I think my compromise of 4ppm for now should probably work just as well. I can always dial it back an additional ppm if things goes well. I am really doing all this to make a dent in my TDS without compromising the current _state_ of my plants.  

Thanks for the feedback.

Cheers,
Michael


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