Kalk in RODI vs Saltwater

[LadyTang2]

Hi!

I am wondering about the difference between dissolving kalk in saltwater vs RODI. Can you dissolve more in RODI and that is superior? Overall should one only do it in RODI?

 

[Cell]

Not sure about solubility differences but with RODI you can add it as the tank water evaporates. If mixed in salt water, you would have to add it during water changes only.

 

[Pntbll687]

Hi!

I am wondering about the difference between dissolving kalk in saltwater vs RODI. Can you dissolve more in RODI and that is superior? Overall should one only do it in RODI?

Most people add kalk to rodi and use it as water evaporates from the system.

You could add kalk to saltwater if you were doing a water change, but you may get some precipitate.

 

[Randy Holmes-Farley Verified Community Expert]

You CANNOT mix it into salt water. You will instantly precipitate magnesium hydroxide and calcium carbonate.

 

[LadyTang2]

You CANNOT mix it into salt water. You will instantly precipitate magnesium hydroxide and calcium carbonate.

But it's eventually going to dumped into a tank of saltwater anyway? Does it not do this in the tank due to the lower concentration of kalk in RODI?

 

[Randy Holmes-Farley Verified Community Expert]

But it's eventually going to dumped into a tank of saltwater anyway? Does it not do this in the tank due to the lower concentration of kalk in RODI?

Correct. You only add a tiny amount to the tank, so the rise in pH, calcium, and alkalinity is much lower.

it’s the same with most alk supplements. They must be dissolved in fresh water not salt water.

 

[HuduVudu]

Hi!

I am wondering about the difference between dissolving kalk in saltwater vs RODI. Can you dissolve more in RODI and that is superior? Overall should one only do it in RODI?

You can dissolve Kalkwasser into salt water. The problem is that you will not have enough carbonic acid to get any kind of real carbonate from it. You may get more when you dose into your tank but you are going to end up with far more calcium than alkalinity unless you have high CO2 levels. Also around 8.5 PH you are going to get calcium carbonate precipitate. This is assuming that you are dosing a small volume and dripping it back into your tank. Dosing your tank directly will drive up the PH to 8.5 (or higher) and as in the small container will start to precipitate over that. It is possible but not very practical.

That said I do do this type of thing, but I put after a very large bicarbonate flow.

 

[HuduVudu]

You CANNOT mix it into salt water. You will instantly precipitate magnesium hydroxide and calcium carbonate.

Not unless your PH is 8.5 or greater, otherwise it behaves near what you see in RO/DI.

 

[Randy Holmes-Farley Verified Community Expert]

Not unless your PH is 8.5 or greater, otherwise it behaves near what you see in RO/DI.

Really? Perhaps you misunderstand the question.

She is asking if you can make a dosing solution from saltwater and calcium hydroxide.

If you dissolve 2 teaspoons of calcium hydroxide into 1 gallon of seawater at pH 8.2, the alkalinity will rise to over 100 dKh, the pH will shoot way, way above 9, and calcium will triple to over 1000 ppm.

Yes, that will INSTANTLY precipitate magnesium hydroxide and calcium carbonate from any pH of stating seawater.

If you misunderstood her question to be whether one can directly dose solid calcium hydroxide to an aquarium, the answer is "yes, but...". Some folks do dose a slurry. It risks precipitation and harsh chemicals landing on organisms before it dissolves, but it is not impossible.

 

[HuduVudu]

If you dissolve 2 teaspoons of calcium hydroxide into 1 gallon of seawater at pH 8.2, the alkalinity will rise to over 100 dKh, the pH will shoot way, way above 9, and calcium will triple to over 1000 ppm.

Ok don't dose 2 teaspoons dose less. Dose what is appropriate to raise the PH to 8.5, or whatever keeps the tank from hard precipitating.

It risks precipitation and harsh chemicals landing on organisms before it dissolves, but it is not impossible.

So we are in agreement.

Also you don't have to dose into the tank you can dose into a sump or dose into a container and then drip. There are many ways to dose.

 

[Randy Holmes-Farley Verified Community Expert]

Ok don't dose 2 teaspoons dose less. Dose what is appropriate to raise the PH to 8.5, or whatever keeps the tank from hard precipitating.

That is way, way too little to be useful as a supplement method.

I have shown that boosting Instant Ocean by 1.4 dKH (6.3 dKH to 7.7 dKH) with hydroxide boosts the pH by 0.66 pH units from 8.10 to 8.76.

Thus, but your assertion, the dosing solution made by mixing seawater and calcium hydroxide cannot raise the alk in the volume by even 1.4 dKH. If you wanted to boost the tank by 1.4 dKh in a day, you'd need to remove the entire tank volume, boost it by 1 dKH, and return it to that tank. That is not a useful supplement.

If that could have been done with a small fraction of the tank volume it might have been useful. But it is not.

 

[Randy Holmes-Farley Verified Community Expert]

So we are in agreement.

Also you don't have to dose into the tank you can dose into a sump or dose into a container and then drip. There are many ways to dose.

I used kalkwasser for 20 years as my only alk and calcium supplement. i like it and think it a fine way to go.

But I do not agree that your assertions are an appropriate answer to the original question by the OP.

 

[HuduVudu]

That is way, way too little to be useful as a supplement method.

I have shown that boosting Instant Ocean by 1.4 dKH (6.3 dKH to 7.7 dKH) with hydroxide boosts the pH by 0.66 pH units from 8.10 to 8.76.

Thus, but your assertion, the dosing solution made by mixing seawater and calcium hydroxide cannot raise the alk in the volume by even 1.4 dKH. If you wanted to boost the tank by 1.4 dKh in a day, you'd need to remove the entire tank volume, boost it by 1 dKH, and return it to that tank. That is not a useful supplement.

If that could have been done with a small fraction of the tank volume it might have been useful. But it is not.

And ... what if you don't want to raise Alk, what if you want to maintain it?

You are making a lot of assumptions about how this might be useful.

If that could have been done with a small fraction of the tank volume it might have been useful.

It can with certain conditions met, but once again you only see one way of doing things and then you argue that one thing with all of your unstated conditions.

 

[HuduVudu]

But I do not agree that your assertions are an appropriate answer to the original question by the OP.

I told the tale with all of the caveats that I am aware of. In fact the original poster liked my explanation, and yes it did answer the last half of her question. By providing useful information to her, I believe she can then make an educated decision about the first half of her post.

And seriously why must you always police people. This is a board and information is shared here. You and I are not the only ones to possess information and whether we think that information is right or wrong is not for us to decide. Present your case and move on.

 

[Crustaceon]

“Say my name”

“Randy Holmes Farley”

“You’re #%^**%% right”

 

[Randy Holmes-Farley Verified Community Expert]

And ... what if you don't want to raise Alk, what if you want to maintain it?

You are making a lot of assumptions about how this might be useful.

I am answering the OP question.
She asked
" I am wondering about the difference between dissolving kalk in saltwater vs RODI. Can you dissolve more in RODI and that is superior? Overall should one only do it in RODI? "

I explained the difference, and explained why EVERYONE dissolves it in fresh water rather than salt water.

Almost no one doses doses solid calcium hydroxide. Many years ago, Anthony Calfo dosed a slurry of calcium hydroxide suspended in fresh water (not salt water). That can work OK, but is not optimal for the reasons I gave.

Can you name anyone who currently doses solid calcium hydroxide dissolved in seawater?
Can you name anyone who currently, regularly doses solid calcium hydroxide directly to a reef tank?

If it is a good thing to do, why is it impossible to find anyone online who currently recommends doing one of both of these?

 

[HuduVudu]

Almost no one doses doses solid calcium hydroxide.

I do.

Would you like to see my tank?

You seriously make to many assumptions and you are way to self assured that you have all the answers.

 

[Randy Holmes-Farley Verified Community Expert]

And seriously why must you always police people. This is a board and information is shared here. You and I are not the only ones to possess information and whether we think that information is right or wrong is not for us to decide. Present your case and move on.

Sorry, that is not the way the Reef Chemistry forum works. I do police everything I read here. That is the idea of the forum and why Reef2Reef wants me here: to ensure accurate information is presented.

Like it or not, that's the deal.

Everyone can present any idea they want.

if I think it incorrect, I will challenged it until the cows come home.

You are welcome to challenge back as long as you want.

 

[Randy Holmes-Farley Verified Community Expert]

I do.

Would you like to see my tank?

You seriously make to many assumptions and you are way to self assured that you have all the answers.

lol
Forgive me if I might request some evidence.

Can you point to a single post you have made prior to today where you say you currently dose calcium hydroxide dissolved in seawater?

 

[LadyTang2]

The answer to my question is RODI, but all this excitement has inspired another question! What if I did continuous auto water changes and I just wanted to boost the alk/ph of my salt mix that has yet to go in tank, just be a little. Would this work?

Maybe this will help me for this add on q, would I get all the ph boost but less alk and less ca? As I add more kalk to saltwater which do I lose and which do I keep from useful forms of Ca Alk and ph? Or is there no amount I can add where I am keeping all 3 and this is a bad idea?