Who is using a conductivity probe for a Kalkwasser Reactor?

[1jwampler]

I have similar Q's in my other post, but, title having pH may be misleading, so started a new thread.
Trying to control Kalkwasser stirring and know when to replace with a probe. Tried pH, works good for monitoring, but, no control du to code limitation in APEX. Others suggested conductivity as a measure. I installed conductivity 3 days ago. Farley suggests that should measure ~10.3mS/cm fully saturated. Highest reading was 9.0 most stable was 8.6 for 12 hours, since then down in the 7s.
Screen Shot 2016-05-20 at 1.17.05 PM.jpg
This graph is from a Geo KR818 ~3 gallons of water, 4 cups of Kalk, tank ATO calls for ~2 gallons/day. pH suggested 12.6 for about a month with new Kalk and water in the KR818 then sliding down to below 12.0 in 3 days, also matched Kalk inability to hold tank pH. Can't get a baseline on Conductivity. Any hints or help would be suggested.

[1jwampler]

Anybody? Thoughts?

[fab]

I'd like to read Randy's article on monitoring kalkwasser concentration to control stirring and to inicate exhaustion. Please post a link to it. Or if it is a thread on Reef2Reef then please link to the post. Thanks.

[1jwampler]

I'd like to read Randy's article on monitoring kalkwasser concentration to control stirring and to inicate exhaustion. Please post a link to it. Or if it is a thread on Reef2Reef then please link to the post. Thanks.

Where did I say Farley wrote an article on kalkwasser concentration to control stirring? Or exhaustion for that matter?

What I asked is what others have used to monitor saturation. Based on another thread I used pH and got lots of feedback saying no use conductivity as pH is unreliable. Not one person who said conducivity would be better has given any input to this, since I installed a conducivity probe and am getting worse results (inconsistent) this with pH.

The above said the Farley article on limewater does conclude that stirring introduces co2 and waiting to stir lime(kalkwasser) can allow it to last virtually forever.

http://www.reefkeeping.com/issues/2005-01/rhf/

Obviously there are limitations to everything, but, I would think anyone using a kalkwasser reactor would want to know the saturation level they are dosing to control time the system is allowed to dose rather than dose base on tank pH and not take into account all of the things that change pH besides kalkwasser. I would also think that people using a reactor would not want to open and clean it more than they have to. By stirring when needed both concerns are met.

So back to the question for this thread, who has done it and how?

[Relethg]

Could be temperature compensation on the probe causing the issue. If it is on and the temp probe is in the DT or sump and your ATO water is different temperature. I use PH probe and only use it to tell when I need to add Kalk. I leave stirrer on all the time. I dose by pushing ATO water through the Stirrer. This keeps the PH at the highest level.

[1jwampler]

Could be temperature compensation on the probe causing the issue. If it is on and the temp probe is in the DT or sump and your ATO water is different temperature. I use PH probe and only use it to tell when I need to add Kalk. I leave stirrer on all the time. I dose by pushing ATO water through the Stirrer. This keeps the PH at the highest level.

Thanks for the input Relethg. What readings are you seeing for pH, when you put in new Kalk and when you believe it's exhausted?

I have now been using the conductivity probe in the reactor for about a month. I would say that it's not possible to stir by it, but, it does give a much quicker indication of a loss of potency/saturation than the pH. I was seeing ~12.5 when new and when it went to 12.4 it would quickly go to 12.3 (<24hrs) then to 12.0 (<48 hours) then in the 11s. I assumed it was saturated even at 12.4 based on Farley's article saying 12.5 was fully saturated, but, not a lot of detail on the graduation down.

The conductivity never hit's Farley's mark of 10.3 mS/cm even when I put 4 cups of BRS Kalk into the approx 4.4 gallon capacity of the Geo KR818. I have seen 10.1 mS/cm but only for a few hours, even with constant stirring, so I assume somewhere in Apex code/probe it's like the pH phone not accurate in anything but seawater. I have opened a case with them on the temperature issue, since no mater how many PM2s (I have 3), if you enable temperature compensation for one probe, they all enable temp compensation. I freaked out, when I turned off compensation on the PM2 for the Kalk reactor, when my tank salinity abruptly went up, I thought oh no, another faulty salinity probe, that Apex would test and say it works fine. But, like every other Apex issue, I either solve it myself or get answers on the forum, and worked backwards and when I removed the Kalk PM2 from the system, I discovered the tank back to normal. So... if my reactor had a port for temperature, I may actually see 10.3 mS/cm, since I have to leave compensation on for (more important) tank data. BTW, no response from Apex, but, I'm not surprised.

Anyhow, the month has proven that average 9.1mS/cm with fresh Kalk goes to mid 8's for about a week, and then declines to 7's after about 2 weeks. I do see less impact to tank pH when I add Kalk that measures in the 7's so I add another cup of Kalk and it stays in the 8's for another week. Something still seems a miss here, as I can't imagine my little 150g tank is using 1 cup of Kalk per week.

I have attached an image of my reeftronics 30 day report, the image is small, so here is the link http://www.reeftronics.net/_/1jwampler/apex-history

Screen Shot 2016-06-19 at 9.12.04 PM.jpg

The conductivity probe does seem to react to changes to the reactor, such as stirring and adding RODI which just like your system feeds the tank ATO. So, from using both, I would say neither pH or conductivity provide great consistency, but, conductivity does provide more information about the condition of the Kalk than pH. So... based on the lack of responses from all the people who said use conductivity, I would say I'm a bit of a test subject, but, I'm learning and it does work better for me. I hope this write up helps others.

Thanks again for your input and response to my thread.

[Relethg]

I have temperature compensation turned on for the reason youstated, it is all or nothing. All probes have it or don’t. Not sure why that isand I have lost confidence in what temperature probe is being used forcompensation. I was under the impression it was the probe on the same module,now I am not sure.
I use the Avast K1 kalk stirrer that can deliver up to 7gallons a day. The manual suggest 1 cup by weekly for the 4500 ML my tank isdosed a day. I found this would not work and would starting going below 11after about 9 days. When I add new Kalk I would get 12.1-12.2 (probe calibratedwith 7.01 and 10.01) and I would add more when it got down to 11. I dose 4500mla day and put 1/3 cup Kalk in the stirrer to start and then 1/3 cup when itgets down to 11. I found that if I start with more it does not last any longer.Never did figure that out. 1/3 cup last about 7-9 days with this set up. Icheck alk daily right now and found this maintains an even number for me 7.5-8DKH. If I let it go below 11 alk would start to fall. I never even consideredturning the stirrer on and off, as I want to keep the water fully saturated andnot cycling. I think constantly starting and stopping is harder on the motor.

[clsanchez77]

Hey guys, are you all still doing this? I also have an Avast K1 and just picked up my second PM2 to monitor the reactor saturation. What calibration fluid did you use on the conductivity probe since the levels are much lower than the tank? My kalk reactor and sump are in the cabinet next to each other so as for temp compensation, I will just let the calculations assume both are at tank temperature. Thanks

[emvanburen]

I’m doing this. Just added a pm2. Conductivity is at 7.3 us/cm with Kalk loaded. Will see how this tracks with depletion.


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