Precipitate in kalk dosing container

[Reef_Hobbyist]

Hi Randy, I am doing using a fully saturated kalk solution. I add a little more kalk than can be fully dissolved so there is some undissolved kalk sitting on the bottom of my 55 gallon dosing container. I figured this was OK because in one of your articles you had described; "any calcium and hydroxide that is taken away via precipitation to form calcium carbonate is replaced by dissolution of more solid lime from the bottom". Is that the same thing as what I am describing?

I have a powerhead sitting on the bottom of my 55g container. When it comes time to refill my dosing container, I fill it with RODI, turn on the powerhead and add more kalk. Before I add more kalk, I can see that the powerhead is stirring up the undissolved kalk (along with whatever else has precipitated out). I let it run until it is fully mixed and then I let it settle out until it is clear again.

Although there is solid kalk sitting on the bottom, you explained there are impurities that also settle out on the bottom. My question is, does my approach stir up these impurities and put them back into solution or do they settle out again and not harm anything? Would it be better to try to mix up each new batch without disturbing the bottom (not even sure that is possible)?

 

[Randy Holmes-Farley]

Your approach sounds fine and is exactly what I do (although I use a length of rigid tubing to stir in the 44 gallon brute cans rather than a powerhead, but a powerhead is fine). I also monitor the conductivity to monitor the potency and know how long I need to stir and/or add more calcium hydroxide.

The impurities will likely just settle out again after stirring up.

 

[Reef_Hobbyist]

Your approach sounds fine and is exactly what I do (although I use a length of rigid tubing to stir in the 44 gallon brute cans rather than a powerhead, but a powerhead is fine). I also monitor the conductivity to monitor the potency and know how long I need to stir and/or add more calcium hydroxide.

The impurities will likely just settle out again after stirring up.

Are you using a conductivity probe and watching it as you stir?

Do you add more kalk than you need and just stop stirring when you reach the potency you want leaving the rest of the undissolved kalk sitting on the bottom of the brute can?

Are you saying that the potency declines without adding more RODI and you give it a stir to mix up some of the undissolved kalk on the bottom to bring the potency back up again? Or do you mean when you add RODI that is the time when you have to add more kalk?

How long do you typically have to stir? Curious to compare that to the powerhead.

 

[Randy Holmes-Farley]

Yes, I drop a conductivity proe into the water as I stir it. 10 mS/cm is about saturation, and I aim for 8+ mS/cm.

I intentionally stir up the muck, and only add more calcium hydroxide if it doesn't seem likely to hit my conductivity target. I don't measure the solids. I just dump a bunch.

I usually stir for 5 minutes or so, but then it swirls longer after that and settles overnight.

The potency stays steady until I add more RO/DI water all at once at the end of a month or so.

 

[Reef_Hobbyist]

Yes, I drop a conductivity proe into the water as I stir it. 10 mS/cm is about saturation, and I aim for 8+ mS/cm.

I intentionally stir up the muck, and only add more calcium hydroxide if it doesn't seem likely to hit my conductivity target. I don't measure the solids. I just dump a bunch.

I usually stir for 5 minutes or so, but then it swirls longer after that and settles overnight.

The potency stays steady until I add more RO/DI water all at once at the end of a month or so.

Interesting.... I have an Apex conductivity probe that I used to measure salinity and a TDS meter for my RODI system. I also see various probes online that can measure conductivity, salinity and TDS with various readouts including µS, mS, ppm, ppt, mg/L, g/L, °C, and °F. Before I "probe" into it any further, what do you recommend?

 

[Randy Holmes-Farley]

The APEX probe will work fine, but the TDS meter may not read high enough.

I use a Pinpoint meter and a more expensive Orion 128 meter

 

[Reef_Hobbyist]

I like the idea of putting an apex probe in there because it would show up nicely on my display and even graph it for me.

However, since it is calibrated for normal seawater, I wonder if it will be able to accurately handle such a low salinity. A fully saturated solution at 10 mS/cm is only 5.627 ppt.

 

[Randy Holmes-Farley]

I like the idea of putting an apex probe in there because it would show up nicely on my display and even graph it for me.

However, since it is calibrated for normal seawater, I wonder if it will be able to accurately handle such a low salinity. A fully saturated solution at 10 mS/cm is only 5.627 ppt.

I do not know if this is what you are using, but it seems to be able to handle the range:

https://www.neptunesystems.com/downloads/docs/PM2_manual.pdf

 

[Reef_Hobbyist]

I do not know if this is what you are using, but it seems to be able to handle the range:

https://www.neptunesystems.com/downloads/docs/PM2_manual.pdf

Yes that is the one. Thanks

 

[Randy Holmes-Farley]

I'd try it and see what you get.

 

[Reef_Hobbyist]

I'd try it and see what you get.

I will give it a try. Any concerns leaving the probe sitting in a high pH solution like that?

 

[Randy Holmes-Farley]

I will give it a try. Any concerns leaving the probe sitting in a high pH solution like that?

Limewater pH will be fine.