Why is my kalkreactor potency declining rapidly

tenurepro

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I just cleaned my kalk reactor, but the potency of my slurry is declining very rapidly - any idea what is causing this?

I have am avast marine k1 kalkwasser reactor. typically i fill that up with aobut 50 to 100 ml of kalk powder (ESV) - (sorry i measure my kalk by pouring it into an empty 50 ml conical tube and adding this tube to the reactor). This usually keeps the ph inside the reactor for 12-11.5 for a good week or so.
Yesterday i took the kalk reactor offline and cleaned it, and removed any of the powder in the bottom. I filled it out with cold RODI water (45f) put it back online in the sump (water temp is 78f) and adding 2 tubes of kalkwasser; this raised the ph quickly to 12, but then it declined to below 11 in the span of a couple of hours. i then added 2 more conicals of kalkwasser. PH went to 12 again for a couple of hours, but then decline quickly to below 10. I added two more conicals this morning and again it only momentarily went to 12 then decline again. Water in the kalk reactor looks normal (whitish), and i see kalk at the bottom of the reactor.

The reactor is fed with a continuous doser kamoer at about 4 ml/min with RODI water.

Not sure why the potency is declining so quickly... is it air in the reactor ? is it related to temp of RODI water initially used to fill reactor. Should i just keep adding kalk ?

thanks for your help... not really understanding what is causing this...

Screen Shot 2022-06-22 at 10.57.59 AM.jpg

as an aside - i am not sure if this is realted but my tank's PH dipped as well after the clean up, but i am thinking this is a cuase of the unsaturated kalk in the reactor vs. something external affecting the PH in both the tank and kalk reactor... Screen Shot 2022-06-22 at 11.02.46 AM.jpg
 
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tenurepro

tenurepro

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pH is only a very crude way to gauge potency. A drop of 0.3 pH units is a 50% drop in potency.
So I am seeing a 1 ph drop in the reactor within a couple of hours? Can’t be consumption I would think… any other factors that can reducing the potency of the slurry ?
 

bnord

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Just listened to a great ReefBum podcast yesterday with Chris Wood. He makes an excellent case for the need to limit the powdered and suspended forms to ambient air as much as possible as the interaction with particularly high levels of room CO2 can and interact with the Kalk and presumably lower its potential
Am a biologist, not a chemist, but it made enough sense to me to and parafilm to the open port on my reservoir of kalk
 
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Wiskey

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My understanding (and I don't have a source for this I just remember reading it somewhere) is that if Kalk Powder is exposed to air for too long it can loose it's potency. Like not just the mixed up lime water, but the powder itself if not properly sealed and stored can become less effective. Maybe your pouch of powder didn't get sealed all the way last time? Maybe try a new unopened bag?

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Biologic

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Not to cofound and complicate the answer, I have some really really old BRS kalkwasser from 2015 that I am using. It's been stored in an attic. Opened repeatedly recently since I have been using it.

I mixed up 5 gallons of saturated kalkwasser into a bucket and I dose it in over the course of a week. My pH of the solution is about 12.09, which in my eyes is pretty good for kalkwasser that old. I have some of their new Pharmagrade kalkwasser coming in and I am curious to see what very new kalkwasser measures up to.

Maybe a bad pH probe?

Also, CO2 is a huge factor in pH, which I am sure you know. Tracking CO2 via my Apex now.


IMG_E90735A9B419-1.jpeg
 

Randy Holmes-Farley

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Just listened to a great ReefBum podcast yesterday with Chris Wood. He makes an excellent case for the need to limit the powdered and suspended forms to ambient air as much as possible as the interaction with particularly high levels of room CO2 can and interact with the Kalk and presumably lower its potential
Am a biologist, not a chemist, but it made enough sense to me to and parafilm to the open port on my reservoir of kalk

It is certainly true that one wants to limit the entry of CO2, and is a reason to not continually stir settled reservoirs of limewater (kalkwasser) such as in a Brute can.
 

Randy Holmes-Farley

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Not to cofound and complicate the answer, I have some really really old BRS kalkwasser from 2015 that I am using. It's been stored in an attic. Opened repeatedly recently since I have been using it.

I mixed up 5 gallons of saturated kalkwasser into a bucket and I dose it in over the course of a week. My pH of the solution is about 12.09, which in my eyes is pretty good for kalkwasser that old. I have some of their new Pharmagrade kalkwasser coming in and I am curious to see what very new kalkwasser measures up to.

Maybe a bad pH probe?

Also, CO2 is a huge factor in pH, which I am sure you know. Tracking CO2 via my Apex now.


IMG_E90735A9B419-1.jpeg

Regardless of the age (almost), you can see what the pH of saturated kalkwasser is on your probe by dissolving/suspending a large amount in a small volume of RO/DI. Like a few teaspoons in a cup.
 
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Randy Holmes-Farley

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So I am seeing a 1 ph drop in the reactor within a couple of hours? Can’t be consumption I would think… any other factors that can reducing the potency of the slurry ?

What does that mean?

pH 12 to pH 11 inside the reactor?
 

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