When do you add more calcium hydroxide to Kalk stirrer?

[ScottB]

My pH has always been 7.9 to 8.1 or so. I bought a Kalk stirrer to offset the added CO2 coming from my calcium reactor to see if I could bump it up a tad. I've been going slow, increasing the amount dosed (via APEX DOS) every few days.

I began with the recommended 150 grams of calcium hydroxide and have dosed about 5 gallons by now. The color of the solution remains roughly the same. Fairly clear at the top, and milkier below with a 1/4 inch or so of undissolved particulate on the bottom.

How do you know when it is time to add more calcium hydroxide? How do you know how much to add? Do I just dump it out and mix new?

The volume of the stirrer is about 6.5 gallons. Reef Octo 250.

Perhaps this thread belongs in the Equipment forum but thought I would start here. Thanks.

 

[Montiman]

I add when I visually see that there is not much left in the stirer. I like there to always be some slushy like kalk at the bottom. If you can't see well or would like a more exact way of measuring. Then you can use a pH or EC probe. I have never tried the EC probe but with my pH probe I add kalk whenever I notice the pH drop. Kalk should be at 12.3 pH but in my experience most of the probes don't read super accurately this high. Mine fluctuates between 11.8 and 12.5 but as soon as it is running low I know because I get a quick drop to 11 or lower.

 

[ScottB]

I add when I visually see that there is not much left in the stirer. I like there to always be some slushy like kalk at the bottom. If you can't see well or would like a more exact way of measuring. Then you can use a pH or EC probe. I have never tried the EC probe but with my pH probe I add kalk whenever I notice the pH drop. Kalk should be at 12.3 pH but in my experience most of the probes don't read super accurately this high. Mine fluctuates between 11.8 and 12.5 but as soon as it is running low I know because I get a quick drop to 11 or lower.

Ah, so kalkwasser at 12.3 pH is what is called "fully saturated" then I guess? I keep reading that phrase in other threads.

The Reef Octo stirrer vessel is made of clear acrylic so I can see top to bottom. It is actually a really nicely designed and built piece of equipment. Not cheap though.

And there does remain about 1/4 inch of white sludge in the bottom. But I will drop my pH probe into a sample of effluent and see what I get.

Thank you Monti.

 

[ScottB]

Came across this thread just now.

Calcium Hydroxide Reactor Question

Hi, I built a stirring-type calcium hydroxide reactor (it sits on a stir plate with a rare earth magnet stir bar) that is 40" tall out of 4" diameter PVC with an integral pH probe. I typically add one cup of fresh calcium hydroxide (from BRS, purchased approximately 2 months ago) to the reactor...

www.reef2reef.com

Interesting. Here is a quote from @Randy Holmes-Farley

While conductivity is the best way to gauge potency (10.3 mS/cm is saturated at 25 deg C), pH can be crudely used.

I can't just drop my APEX conductivity probe into a sample though can I? It measures in PPT.

Should I go with something like this?

Multi-variable Water Quality Testers | Omega Engineering

The PHH-7000 Series feature replaceable sensors. Each kit comes in a carrying case with buffer or standard solutions for calibration. Click here for more

www.omega.com

 

[sandfan85]

Stirrer’s like the Avast Marine have a Ph probe holder built in. This is so you can watch the saturation rate. A fully saturated solution is 12.3. As the kalk is used it will drop. At that point you just add more. Thats what’s so awesome about stirrers, you can’t add too much. It will only mix to the fully saturated level. No need to dump and start over. Be sure to allow it to settle before continuing to dose. Your stirrer should be pulling from the top of your saturated solution.

 

[ScottB]

Stirrer’s like the Avast Marine have a Ph probe holder built in. This is so you can watch the saturation rate. A fully saturated solution is 12.3. As the kalk is used it will drop. At that point you just add more. Thats what’s so awesome about stirrers, you can’t add too much. It will only mix to the fully saturated level. No need to dump and start over. Be sure to allow it to settle before continuing to dose. Your stirrer should be pulling from the top of your saturated solution.

Thank you. Good info.

Jeez I spent a fortune on this Reef Octo 250 stirrer but got no probe. Otherwise though, it is very nicely constructed.

As reported on another thread, I found a significant part of my problem. My APEX DOS quit pushing RODI into the stirrer. Even though I have all these wonderful dosing charts & reports, the dosing heads haven't spun for a week or more. Always something.

 

[Dennis Cartier]

As others have mentioned, use EC to measure fully saturated. Measuring the PH will not be effective as saturation drops majorly before the PH does.

For your Reef Octopus stirrer, and for any other ones which lack a probe port, you can add an EC or TDS meter inline with a tee. The HM Digital ones are dirt cheap and work great for this. The EC version of their meter only goes to 10 mS/cm but is close enough to give you a good idea when the solution is weakening. On the EC, fully saturated will read 999 with the x10 illuminated.

For the HM TDS meter, they use a formula to convert EC to TDS, so the TDS reading of fully saturated is about 515 ppm with the x10 illuminated.

I suggest getting a baseline reading of fully saturated kalk on the HM meter and then just keep an eye on the reading from there. As Randy has said, the reading will decrease linearly in relation to saturation.

Dennis

 

[andrewb70]

Hi, watched a Reefbum video where he has his Kalk in a 30 gallon storage tub and doses via a GHL doser - he says he doesn't stir it and that as long as there's Kalk sediment in the bottom he just tops it up as required. The only thing is of course having the space for such a tub but I didn't realize Kalk doesn't need stirring. Just my 2 cents

 

[ScottB]

As others have mentioned, use EC to measure fully saturated. Measuring the PH will not be effective as saturation drops majorly before the PH does.

For your Reef Octopus stirrer, and for any other ones which lack a probe port, you can add an EC or TDS meter inline with a tee. The HM Digital ones are dirt cheap and work great for this. The EC version of their meter only goes to 10 mS/cm but is close enough to give you a good idea when the solution is weakening. On the EC, fully saturated will read 999 with the x10 illuminated.

For the HM TDS meter, they use a formula to convert EC to TDS, so the TDS reading of fully saturated is about 515 ppm with the x10 illuminated.

I suggest getting a baseline reading of fully saturated kalk on the HM meter and then just keep an eye on the reading from there. As Randy has said, the reading will decrease linearly in relation to saturation.

Dennis

Thanks Dennis, very helpful.

This is the only HM inline EC I saw on Amazon. On the readout, I don't see a 10X indicator on the display, nor a toggle. Is this suitable? The one on BRS (for $20 more) looks pretty much the same.

 

[Randy Holmes-Farley]

pH is a poor way of measuring saturation of limewater (kalwkasser).

pH 11.8 is super weak limewater.

Fully saturated is pH 12.54 at 25 deg C. Higher at lower temps and lower at higher temps.

Each 0.3 pH unit drop from there is about a 50% drop in potency.

Thus, pH 12.24 is only about 50% saturated. pH 11.8 is less than 25% saturated.

If you choose to use pH for this purpose, be sure to calibrate the ph meter with truly saturated limewater (lots of extra solids in a cup of RO/DI) to 12.54.

 

[Randy Holmes-Farley]

Thanks Dennis, very helpful.

This is the only HM inline EC I saw on Amazon. On the readout, I don't see a 10X indicator on the display, nor a toggle. Is this suitable? The one on BRS (for $20 more) looks pretty much the same.

That one reads to 10 mS/cm. Saturation is about 10.3 mS/cm. It is likely OK for this purpose, but not perfect.

 

[ScottB]

That one reads to 10 mS/cm. Saturation is about 10.3 mS/cm. It is likely OK for this purpose, but not perfect.

Well it is installed. Along with my repaired APEX DOS finally. Reminder, this is :

https://m.media-amazon.com/images/I/41s7UYFAqaL._AC_AC_SR98,95_.jpg

Not perfect indeed. On the bright side the RODI coming in reads zero but on the downside I have no idea what to make of this number. I should say that holding the dose open after priming seems to be holding pH at at an abnormally high level for the faint lighting at 21:00 hours. Without Kalk I typically flatline around 8pm

Here is my readout. This is 4 week old solution in my stirrer with plenty of slurry on the bottom.

 

[Dennis Cartier]

Scott, as a test, I would mix up a fully saturated kalk solution and submerge one of the probes in it. I would expect it to read about 999 or 990 with a x10 indicator lit up on the display. That would be reading 9.99 or 9.90 mS/cm. Then you can compare it to the reading you are getting.

Is the reading of 61uS/cm on the output of your kalk stirrer? For comparison, fully saturated should be 10,300 uS/cm.

Dennis

 

[ScottB]

Scott, as a test, I would mix up a fully saturated kalk solution and submerge one of the probes in it. I would expect it to read about 999 or 990 with a x10 indicator lit up on the display. That would be reading 9.99 or 9.90 mS/cm. Then you can compare it to the reading you are getting.

Is the reading of 61uS/cm on the output of your kalk stirrer? For comparison, fully saturated should be 10,300 uS/cm.

Dennis

Thanks Dennis. Yes this was the output from the stirrer. The input to the stirrer was 0.

I will mix a cup and test this afternoon, and report back.

 

[ScottB]

Thanks Dennis. Yes this was the output from the stirrer. The input to the stirrer was 0.

I will mix a cup and test this afternoon, and report back.

I tested again this morning with effluent passing through this time and got 561 with the 10X indicator flashing. I have dumped that all out now.

I tested with the probe 1 gallon & 2 level teaspoons (according to ESV instructions) and only got a reading of 661. Maybe I did not let it sit long enough?

 

[Randy Holmes-Farley]

I tested again this morning with effluent passing through this time and got 561 with the 10X indicator flashing. I have dumped that all out now.

I tested with the probe 1 gallon & 2 level teaspoons (according to ESV instructions) and only got a reading of 661. Maybe I did not let it sit long enough?

Try putting 2 teaspoons in a CUP of RO/DI water, mix for a few min, and see what you get. That's how to ensure saturation.

 

[ScottB]

Try putting 2 teaspoons in a CUP of RO/DI water, mix for a few min, and see what you get. That's how to ensure saturation.

Sorry tardy in responding. Well that certainly measured saturation. It quickly counted up into the 900 range before producing an an out of range "ERR".

So I emptied the old solution and dumped in a truckload of kalk. Given the current temp and air quality I don't have a good pH baseline but I am pumping in the kalk but not much gain to report just yet.

 

[Dennis Cartier]

Sorry tardy in responding. Well that certainly measured saturation. It quickly counted up into the 900 range before producing an an out of range "ERR".

So I emptied the old solution and dumped in a truckload of kalk. Given the current temp and air quality I don't have a good pH baseline but I am pumping in the kalk but not much gain to report just yet.

That is great, that it is able to approach the saturation point. I think that saturation should have been 1030, so if it errors out after 990, then you should be fine to use it with your stirrer. You will probably not be able to push it back into error state during normal use, and seeing how close it is to the end of it's range will still help you to detect the 'life' left in the kalk surplus within your reactor.

Dennis

 

[Randy Holmes-Farley]

Sorry tardy in responding. Well that certainly measured saturation. It quickly counted up into the 900 range before producing an an out of range "ERR".

So I emptied the old solution and dumped in a truckload of kalk. Given the current temp and air quality I don't have a good pH baseline but I am pumping in the kalk but not much gain to report just yet.

Thanks for the update!

 

[ScottB]

I think we are finally on to something folks! With the heat around here, CO2 kept building with all the windows shut. It was not a pretty trend line but I think we are getting there. Thanks for the help!

I suppose I should be tracking ALK during this transition to make sure it does not increase too much, right?