# PPS Pro fert solution replace potassium nitrate with calcium nitrate?



## darthmilmo (Feb 19, 2013)

Why don't you order them online??? There are even sellers in this forrum.

Anyway, plants need potassium, more so then calcium. It's like saying I don't have fresh water, I only have salt water. How many cups of salt water should I drink a day?


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## poissonej (Jan 17, 2014)

It's illegal in my country to buy/sell it or import it unless you have a license


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## Darkblade48 (Jan 4, 2008)

You can use calcium nitrate if you wish, but note that the effective dose of nitrates will be double that of potassium nitrate.

In addition, note that you will be increasing your GH by dosing calcium nitrate.


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## poissonej (Jan 17, 2014)

Thanks! My tap water is very soft, so it wouldn't hurt to bring up the GH a bit, I think. I suppose then that adding 32.5 g (as opposed to 65 g of potassium nitrate) will give the equivalent dose of nitrate?


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## Darkblade48 (Jan 4, 2008)

poissonej said:


> I suppose then that adding 32.5 g (as opposed to 65 g of potassium nitrate) will give the equivalent dose of nitrate?


No. You have to account for the different molecular weights of potassium and calcium.


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## nilocg (Jul 12, 2010)

500mg of Ca(no3)2.4H20 will raise 10g of water ~7ppm no3


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## happi (Dec 18, 2009)

*just a heads up, cano3 will react with any SO4 in the solution. if you want i can give you a recipe which creates KNO3 by reacting CANO3 and K2SO4.*


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## Darkblade48 (Jan 4, 2008)

happi said:


> *just a heads up, cano3 will react with any SO4 in the solution. if you want i can give you a recipe which creates KNO3 by reacting CANO3 and K2SO4.*


Simple single displacement reaction, but why would you want to waste the potassium sulfate in that way?


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## happi (Dec 18, 2009)

Darkblade48 said:


> Simple single displacement reaction, but why would you want to waste the potassium sulfate in that way?


actually nothing really goes to waste beside so4 will fall from the solution, so4 isn't needed in big amounts anyway, you will be left behind with KNO3 in the solution with whatever K+ levels you choose.


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## Darkblade48 (Jan 4, 2008)

happi said:


> actually nothing really goes to waste beside so4 will fall from the solution, so4 isn't needed in big amounts anyway, you will be left behind with KNO3 in the solution with whatever K+ levels you choose.


Well, the calcium sulfate precipitates out, as it is relatively insoluble (though compared to other calcium salts, quite soluble), so there is quite a bit of waste.

Sulfur is considered a macronutrient for plants, but in general, not much emphasis is placed on it because it is generally abundant.


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## Diana (Jan 14, 2010)

And the OP said the GH was on the low side, anyway, so the added Ca is good in this case.


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## Zorfox (Jun 24, 2012)

happi said:


> *just a heads up, cano3 will react with any SO4 in the solution. if you want i can give you a recipe which creates KNO3 by reacting CANO3 and K2SO4.*


You can list that recipe. I've never heard of doing that. Some countries allow calcium nitrate but not potassium nitrate. Besides it's just a neat thing to know even though I will probably never need it lol


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## Darkblade48 (Jan 4, 2008)

Zorfox said:


> You can list that recipe. I've never heard of doing that. Some countries allow calcium nitrate but not potassium nitrate. Besides it's just a neat thing to know even though I will probably never need it lol


Ca(NO3)2 + K2SO4 --> 2KNO3 + CaSO4

1 mole of calcium nitrate and potassium sulfate generates 1 mole of calcium sulfate and 2 moles of potassium nitrate.

From there, it's a simple exercise to work out the masses of each required.


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## plantbrain (Dec 15, 2003)

OP is from SG, which bans KNO3 sales. Dr Mallick's (in SG)use to carry it, not sure if he still does.

Hence the idea of using Ca(NO3)2.

SG's tap is rather nice and pure, but many do not add GH and still quite well.
Adding a GH booster will not hurt.

Since you are adding Ca(NO3)2 to the water and K2SO4 to the water, why does it not also precipitate in the aquarium?


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## Diana (Jan 14, 2010)

> Since you are adding Ca(NO3)2 to the water and K2SO4 to the water, why does it not also precipitate in the aquarium?


Maybe it does, but the dose is so low you cannot see it.


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## happi (Dec 18, 2009)

Diana said:


> Maybe it does, but the dose is so low you cannot see it.


+1 on what Diana said, sometime it takes a few days for it to complete its reaction, when you make the solution for the first time, it will start to react immediately and it will continue to react slowly for few days to week. in aquarium the reaction cannot be seen because reaction is slow and precipitate cannot be seen by naked eyes due to bigger volume of the water.



Zorfox said:


> You can list that recipe. I've never heard of doing that. Some countries allow calcium nitrate but not potassium nitrate. Besides it's just a neat thing to know even though I will probably never need it lol


*Calcium nitrate 10 gram
K2SO4 30 Gram
*
i have used this with great success so far, the reaction will precipitate out the SO4 and the solution become Highly concentrated KNO3 with high K+, the recipe is just to give you an example and you can increase or decrease the amount as long as the ratio stays about the same. however, this recipe might not be causing the 100% reaction because i am sure you could cause better reaction by increasing or decreasing those two chemicals, but so far it has worked for me without any issue.


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## Darkblade48 (Jan 4, 2008)

plantbrain said:


> Since you are adding Ca(NO3)2 to the water and K2SO4 to the water, why does it not also precipitate in the aquarium?





Diana said:


> Maybe it does, but the dose is so low you cannot see it.





happi said:


> +1 on what Diana said, sometime it takes a few days for it to complete its reaction, when you make the solution for the first time, it will start to react immediately and it will continue to react slowly for few days to week. in aquarium the reaction cannot be seen because reaction is slow and precipitate cannot be seen by naked eyes due to bigger volume of the water.


As mentioned previously, calcium sulfate, while being relatively insoluble, is still soluble (Ksp is only on the order of -5). In the large amount of water that aquariums typically are, there is no problem of trying to dissolve all of it. In addition, as it happens in such a large volume, if it does precipitate, it would appear as a slight haze, and probably not visible.

I would not say that it would take several days to complete, however. Single displacement reactions are usually rather quick. 



happi said:


> *Calcium nitrate 10 gram
> K2SO4 30 Gram
> *
> i have used this with great success so far, the reaction will precipitate out the SO4 and the solution become Highly concentrated KNO3 with high K+, the recipe is just to give you an example and you can increase or decrease the amount as long as the ratio stays about the same. however, this recipe might not be causing the 100% reaction because i am sure you could cause better reaction by increasing or decreasing those two chemicals, but so far it has worked for me without any issue.





Darkblade48 said:


> Ca(NO3)2 + K2SO4 --> 2KNO3 + CaSO4
> 
> 1 mole of calcium nitrate and potassium sulfate generates 1 mole of calcium sulfate and 2 moles of potassium nitrate.


The above ratio will work, but you have a large excess (almost 3 times) of potassium sulfate. You would have a solution rich in potassium, nitrate, and relatively rich in sulfates.

Do note that the reaction does not precipitate out "sulfates," it precipitates out calcium sulfate.


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## happi (Dec 18, 2009)

Darkblade48 said:


> As mentioned previously, calcium sulfate, while being relatively insoluble, is still soluble (Ksp is only on the order of -5). In the large amount of water that aquariums typically are, there is no problem of trying to dissolve all of it. In addition, as it happens in such a large volume, if it does precipitate, it would appear as a slight haze, and probably not visible.
> 
> I would not say that it would take several days to complete, however. Single displacement reactions are usually rather quick.
> 
> ...


yes that is correct, it form Ca sulfate and it does take a few days for the reaction to complete in the solution, i have seen it continue to react for few days because i would filter out most of the Ca sulfate from the solution, at some point it would finally stop to react further. the CaSO4 in the solution will not mix with the solution, it will just sit there on the bottom, when you add the solution to the aquarium, you are really only adding K+ and NO3, unless you shake the solution which might add some Caso4 to the tank otherwise so4 sits on the bottom.



Darkblade48 said:


> Do note that the reaction does not precipitate out "sulfates," it precipitates out calcium sulfate.


yeh but isn't that formed by reaction of SO4 and Ca in the solution from CAno3 and K2so4, what you are left with is KNO3 here and rest of the Caso4 sitting at the bottom in powder/paste form which can be filtered out, the solution is only KNO3 and no SO4 in the liquid form.


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## JoraaÑ (Jun 29, 2009)

OP...look here


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## Darkblade48 (Jan 4, 2008)

happi said:


> yes that is correct, it form Ca sulfate and it does take a few days for the reaction to complete in the solution, i have seen it continue to react for few days because i would filter out most of the Ca sulfate from the solution, at some point it would finally stop to react further.


You must remember, that all reactions can be modeled as an equilibrium. If you were to leave the precipitate inside, then the reaction has reached an equilibrium state. However, by removing the precipitate, you are promoting conditions for further precipitation of the calcium sulfate (shift to the right side of the reaction).

Thus, it may *seem* like the reaction takes several days to move to completion, but in reality, it happens relatively quickly. 



happi said:


> the CaSO4 in the solution will not mix with the solution, it will just sit there on the bottom,


As mentioned, the Ksp of calcium sulfate is on the order of -5. There will be a certain amount that can dissolve into the water column, given enough time, and water volume. 



happi said:


> when you add the solution to the aquarium, you are really only adding K+ and NO3, unless you shake the solution which might add some Caso4 to the tank otherwise so4 sits on the bottom.


As I previously mentioned, your masses that you used for the reaction provides an excess of potassium sulfate. This means you will have leftover, unreacted potassium sulfate in solution. You will be adding sulfates, to some degree (contributed by the potassium sulfate).

As I also previously mentioned, the precipitate that you see is not just "sulfate," as it is just an anion that does not exist by itself.




happi said:


> yeh but isn't that formed by reaction of SO4 and Ca in the solution from CAno3 and K2so4, what you are left with is KNO3 here and rest of the Caso4 sitting at the bottom in powder/paste form which can be filtered out, the solution is only KNO3 and no SO4 in the liquid form.


Again, as you are adding in an excess of the potassium sulfate, there will be excess unreacted sulfate that is left in solution (contributed by the potassium sulfate). Furthermore, there will also be some calcium sulfate in the solution (minute, but present).


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## plantbrain (Dec 15, 2003)

Diana said:


> Maybe it does, but the dose is so low you cannot see it.


Okay, hehe, now since there's virtually always some Ca++ in the tank, and.........we add a fair amount of K+..........why is there still Ca++ present?
Even my non CO2 tanks have Ca++ after 2 weeks post dosing of both nutrients.

So this does not answer the question. :icon_idea

If we need to wait weeks or more, then it's a non issue.
Days?

Hours? 

How many?

Should we just wing it and guess, then make such statements?
Not seen a single post that says much here.


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## Darkblade48 (Jan 4, 2008)

plantbrain said:


> Okay, hehe, now since there's virtually always some Ca++ in the tank, and.........we add a fair amount of K+..........why is there still Ca++ present?
> Even my non CO2 tanks have Ca++ after 2 weeks post dosing of both nutrients.
> 
> So this does not answer the question. :icon_idea


What exactly is the question? You can dose potassium sulfate and load up the water column with potassium, but it will not force calcium to precipitate out (calcium sulfate is relatively insoluble, but not completely insoluble). 

Calcium cations, potassium cations, and sulfate anions can all exist happily in the water column.

Furthermore, it is unlikely that the water in an aquarium will be a completely saturated solution.


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## poissonej (Jan 17, 2014)

@Joraan: Thanks for the link!

And tbh the rest of this flew way over my head haha. Could someone be kind enough to distill the gist of what I need to know if I were to use calcium nitrate in PPS solution, please?


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## Zorfox (Jun 24, 2012)

poissonej said:


> @Joraan: Thanks for the link!
> 
> And tbh the rest of this flew way over my head haha. Could someone be kind enough to distill the gist of what I need to know if I were to use calcium nitrate in PPS solution, please?


What size is your tank poissone?


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## poissonej (Jan 17, 2014)

Zorfox said:


> What size is your tank poissone?


It's 45.1 litres~ Slightly less than 12 gallons


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## Zorfox (Jun 24, 2012)

644mg will raise nitrate 7.5ppm which is a full EI dose. Notice it only raises the GH 0.34 degrees? That's very little. No worries about the extra calcium. 

Element PPM
Ca 2.42
NO3 7.50
dGH 0.34

Since you're not dosing KNO3 you need to add potassium. KNO3 usually provides enough alone. K2SO4 is the most common here.

I would recommend a solution for such a small tank. 644mg is a tiny amount. Unless you want to weigh it every time you dose, solutions would be easier. An example below. One dose will raise levels the same as above.

64.4 grams in 500ml of water. Each dose is 5ml.

EDIT: forgot to add. All those numbers come from this calculator.


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## plantbrain (Dec 15, 2003)

Darkblade48 said:


> What exactly is the question? You can dose potassium sulfate and load up the water column with potassium, but it will not force calcium to precipitate out (calcium sulfate is relatively insoluble, but not completely insoluble).
> 
> Calcium cations, potassium cations, and sulfate anions can all exist happily in the water column.
> 
> Furthermore, it is unlikely that the water in an aquarium will be a completely saturated solution.


Well think about it............you sort of answered the question which goes back the original premise. How much saturation is required before it becomes a dosing problem? Is KH and pH a factor for perciptation? Temp?

Concentration, sure, but what concentration?

Same issue with Fe and PO4.


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## poissonej (Jan 17, 2014)

Zorfox said:


> 644mg will raise nitrate 7.5ppm which is a full EI dose. Notice it only raises the GH 0.34 degrees? That's very little. No worries about the extra calcium.
> 
> Element PPM
> Ca 2.42
> ...


Thanks!  I have K2SO4 on hand too. That calculator is really handy :thumbsup:


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## Darkblade48 (Jan 4, 2008)

plantbrain said:


> Well think about it............you sort of answered the question which goes back the original premise. How much saturation is required before it becomes a dosing problem? Is KH and pH a factor for perciptation? Temp?
> 
> Concentration, sure, but what concentration?
> 
> Same issue with Fe and PO4.


Tom, I'm still not sure what the issue/question is here. As I mentioned, calcium sulfate will not precipitate out in the aquarium because of the large volume of water. The same goes for iron phosphate. 

Of course, other dissolved solutes, pH and temperature will play a role in whether or not precipitate forms.

happi originally was considering mixing potassium sulfate and calcium nitrate (I would assume in a small amount of distilled water) so that the solution because saturated enough to the point that calcium sulfate will precipitate out of solution, leaving potassium, nitrate and a small amount of calcium and sulfate species in solution. 

I also pointed out at this point, that happi's ratios did not follow stoichiometrically, as there was an excess of potassium sulfate used (i.e. less could be used to achieve the same goal).


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## Zorfox (Jun 24, 2012)

A defined concentration required for precipitation would be nice to know. Especially in regards to Fe and PO4. I've dosed both simultaneously many times and have yet to see any precipitate although others claim to see this happen all the time. It's one of those things I simply have no idea why. I've always assumed it was a PH difference, mine is usually high but that's a guess. It would be nice to know for sure.


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## Darkblade48 (Jan 4, 2008)

Well, the Ksp for ferric phosphate (dihydrate) is 9.91 to the -16th magnitude.

Shouldn't be too hard to work it out from there.


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## Zorfox (Jun 24, 2012)

Darkblade48 said:


> Well, the Ksp for ferric phosphate (dihydrate) is 9.91 to the -16th magnitude.
> 
> Shouldn't be too hard to work it out from there.


Maybe for you but I'm not a chemist. I'm more of an application driven chemist. I learn what I need when I need it. I actually was referring to the necessary concentration of Fe and PO4 required for binding. Are you saying once dissolved they won't react?


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## Seattle_Aquarist (Jun 15, 2008)

Darkblade48 said:


> You can use calcium nitrate if you wish, but note that the effective dose of nitrates will be double that of potassium nitrate.
> 
> In addition, note that you will be increasing your GH by dosing calcium nitrate.


Hi poissonej,

+1 for Darkblade's comment that you can use calcium nitrate. Yes, it will raise the dGH of your water but if you are conscientious about your 50% weekly water changes it should not be a problem. The water changes become even more important since you will want to add extra magnesium (I use Epsom Salt/MgSO4) to maintain the approximately 1:4 recommended calcium:magnesium ratio.

10 gallon; no CO2; low [email protected]


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## Darkblade48 (Jan 4, 2008)

Zorfox said:


> Maybe for you but I'm not a chemist. I'm more of an application driven chemist. I learn what I need when I need it. I actually was referring to the necessary concentration of Fe and PO4 required for binding. Are you saying once dissolved they won't react?


I'm not a chemist either (though I have a minor in chemistry).

What do you mean by binding? Do you mean to say precipitation? 

If so, the concentration that is required for precipitation is dependent on several factors.

Dissolution can be modeled as an equilibrium reaction, whereby 

FePO4 <--> Fe+3 + PO4-3 

Whether the equilibrium shifts to the right or left depends on Ksp, other solutes present, concentration of solutes, temperature, etc.

That being said, once (any) chemical is dissolved, it can be forced out of solution if the right conditions are met.


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## Zorfox (Jun 24, 2012)

Darkblade48 said:


> I'm not a chemist either (though I have a minor in chemistry).
> 
> What do you mean by binding? Do you mean to say precipitation?
> 
> ...


Yes, I did mean precipitation. Basically, I was looking for a concentration range that would be conducive to precipitation. I realize other factors impact this. 

After doing a little research I realize this is not a simple process. Fe and PO4 precipitation is only one of many. Far more than I thought occurs when iron is added. It's quite interesting actually.


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## happi (Dec 18, 2009)

Darkblade48 said:


> I'm not a chemist either (though I have a minor in chemistry).
> 
> What do you mean by binding? Do you mean to say precipitation?
> 
> ...


far as i remember Po4 and Fe reaction depend on the PH and Iron Chelate being used. BTW i think we are all started to go off topic now.


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## Zorfox (Jun 24, 2012)

happi said:


> BTW i think we are all started to go off topic now.


I think we passed off topic on the first page of this thread lol. Luckily the OP's questions have been answered. When does it become improper to have a discussion evolve off topic? I personally think if an OP is asking a question that question should be answered before deviating from the original post. After that conversations should be allowed to progress. Every forum is different though.


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## Darkblade48 (Jan 4, 2008)

Zorfox said:


> Yes, I did mean precipitation. Basically, I was looking for a concentration range that would be conducive to precipitation. I realize other factors impact this.
> 
> After doing a little research I realize this is not a simple process. Fe and PO4 precipitation is only one of many. Far more than I thought occurs when iron is added. It's quite interesting actually.


Indeed. As aquarium water is not a pure solvent, there are lots of things that can be going on.

At standard temperature and pressure, given the Ksp of a solute, you can calculate how much of the solute will dissolve, assuming no other effects (common ion, some salts have strange properties in solution, etc).

Just for information's sake, I calculated the solubility to be 4.7 * 10^-6 grams in 1L of water.




happi said:


> far as i remember Po4 and Fe reaction depend on the PH and Iron Chelate being used. BTW i think we are all started to go off topic now.


Yes, we are quite off topic. But this was an interesting turn of events, in any case. And yes, since the iron is chelated in most cases, it is not available to react with phosphate in the water column.



Zorfox said:


> When does it become improper to have a discussion evolve off topic? I personally think if an OP is asking a question that question should be answered before deviating from the original post. After that conversations should be allowed to progress. Every forum is different though.


Difficult to say; I do agree that since the original question has been answered, it should be OK for the topic to deviate a bit. If warranted, we (the moderation team) might just split the thread to start a new thread.


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## poissonej (Jan 17, 2014)

Seattle_Aquarist said:


> Hi poissonej,
> 
> +1 for Darkblade's comment that you can use calcium nitrate. Yes, it will raise the dGH of your water but if you are conscientious about your 50% weekly water changes it should not be a problem. The water changes become even more important since you will want to add extra magnesium (I use Epsom Salt/MgSO4) to maintain the approximately 1:4 recommended calcium:magnesium ratio.
> 
> 10 gallon; no CO2; low [email protected]


Hi! Thanks for the info  Sorry it took so long to reply. 

I do have more questions, but I'm really busy right now that I haven't had time to work them out and ask them; but please continue, I don't mind this going off topic at all! I'll find some time soon to ask more things.


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## Positron (Jul 22, 2013)

You can use calcium nitrate, but I would add some MgSO4 to maintain a proper ca:mg balance. You must also look into another way of getting K into the water. You can use K2SO4 for this.


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## poissonej (Jan 17, 2014)

Thanks for all the help guys! I'm trying to figure out the easiest way to dose all the salts at once, the way PPS is usually dosed. I want to go for a solution, but I'm having trouble figuring out how much of each salt to put into how much distilled water when I use calcium nitrate instead of potassium nitrate, cuz I'm guessing it would mess up things somewhat. Or if I use Ca(NO3)2, would I have to keep it separate from the rest of the salts? I have Ca(NO3)2, K2SO4, KH2PO4, and MgSO4 on hand.


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## Darkblade48 (Jan 4, 2008)

I would keep it separately, since calcium sulfates generally precipitate out rather easily.


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## poissonej (Jan 17, 2014)

Sorry my replies are so sporadic, I've been really busy! 

Anyway, I'm wondering about the rest of the salts. Can I put them into one bottle And dose them all at once? I'm kind of confused about how it works. In the calculator that Zorfox linked me to, I calculated the doses for the other salts:

Magnesium sulfate: 1000 ml bottle, 5 ml dose
To reach your target of 0.1 ppm Mg you will need to add 9.127 g MgSO4.7H2O to your 1000.0 mL dosing container. Add 5.0 mL of that mix to your 45.0 L aquarium to yield
Element	ppm/degree
Mg	0.10
S	0.13
dGH	0.02

Potassium sulfate: 1000 ml bottle, 5 ml dose
To reach your target of 1.33 ppm K you will need to add 26.675 g K2SO4 to your 1000.0 mL dosing container. Add 5.0 mL of that mix to your 45.0 L aquarium to yield
Element	ppm/degree
K	1.33
S	0.55

Monopotassium phosphate: 1000 ml bottle, 5 ml dose
To reach your target of 0.1 ppm PO4 you will need to add 1.651 g K2HPO4 to your 1000.0 mL dosing container. Add 5.0 mL of that mix to your 45.0 L aquarium to yield
Element	ppm/degree
K	0.08
P	0.03
PO4	0.10

Would these figures apply only if I have them in separate 1000 ml bottles? Would it be different if I put them all in one 1000 ml bottle? And how would I figure that out?


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## Zorfox (Jun 24, 2012)

You can mix them all in the same 1,000ml bottle if you wish. The dose is the same for both. I prefer not to for flexibility. The doses you listed are quite small. Are you selecting "The Estimative Index" in the "and I am calculating for" selection? Below are the numbers for a 45 liter tank using full EI dosing; 1,000ml bottle and 5ml dose.

Magnesium (MgSO4.7H2O) = 456.332 g
Potassium (K2SO4) = 150.423 g
Phosphate (KH2PO4) = 16.765 g


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## poissonej (Jan 17, 2014)

I selected PPS, because I'd prefer it over EI~ Thanks! I think if I separate them I'll go for 500 ml bottles just to make things easier to manage


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