calcium reactor controller question

acroholic

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Guys,
I have a question regarding the Milwaukee Instruments SMS 122 pH controller I use to control CO2 delivery to my calcium reactor. I have a GEO 618. System is about 425 net gallons.

I was noticing a gradual KH drop in my tank (got down to 6.8), so I added a second filled media container in line for the effluent of the GEO to pass thru on its way back to the sump. I also calibrated my controller, and found that I could not calibrate the MI pH probe any more, meaning it was time to replace the probe. I did this and calibrated the new probe to the controller, and set the controller off point at about 6.6. But now it seems that the pH in the GEO never goes below 6.7 and the gas is always on, whereas before I replaced the probe the controller would turn the CO2 on and off for definite periods. Bubble count is about 85 bubbles/minute.

That being said, everything seems to be fine. I have tested the KH every day and it seems to be holding at 8.5-9 with a Salifert test kit. I have a pretty large SPS load, as many of my colonies are big now.

Effluent in the GEO at 6.6, and effluent after it passes thru the second media holder is about 6.75, which seems reasonable.

I guess I am wondering if the old pH probe was just so out of calibration that it was reading way too low, turning of the CO2 before it should, thus explaining the decreasing KH of the system, along with the increased KH demand from the big acropora colonies I have now?

It just seemed abnormal to me that the gas would be on almost all the time. No CO2 leaks anywhere I know if.

I also use a Nilsen stirrer to dose kalk, so I wonder if that could be a part of the cause of the CO2 being on all the time as well, meaning the Nilsen spikes the tank water pH, which then goes into the Calcium Reactor, making the controller come on prematurely early?

I'm thinking of taking the Nilsen off line for a bit to see if this new, properly calibrated pH probe turns on and of without the Nilsen running and if it can maintain proper KH without needing to dose Kalk.

So do you guys running Calcium Reactors see definite noticeable off/on periods for your CO2, or are yours on most of the time?
 
I saw noticeable on/off periods with my CA reactor setup, though I only ran it for a short while. I could sit on the couch and watch the pH climb to 6.72, hear the solenoid click, watch the pH drop to about 6.65, the solenoid clicks off, and the pH drops to 6.62 before starting to climb again. The whole cycle took about 30min at 1 bubble per 2 seconds, and dripping the effluent about 30ml/min.
 
Have you confirmed your flow rate has not changed? If your flow rate through the reactor has increased, your 85 bpm might not be enough to get the pH down. It is also possible that your old probe was out of calibration or the new one is calibrated slightly high.

Either way, the best plan of attack is to watch the CA and Alk levels over the next few weeks to see if the stay steady, drop or increase and adjust flow and/or pH accordingly.
 
Schwaggs;559240 wrote: Have you confirmed your flow rate has not changed? If your flow rate through the reactor has increased, your 85 bpm might not be enough to get the pH down. It is also possible that your old probe was out of calibration or the new one is calibrated slightly high.

Either way, the best plan of attack is to watch the CA and Alk levels over the next few weeks to see if the stay steady, drop or increase and adjust flow and/or pH accordingly.

I'll monitor it.

Flow rate thru the reactor has not changed. I have always used about 55 ml/minute, which roughly translates into a fast drip. Almost a stream but not quite.

The 85 bpm CO2 rate is about as high as I can make it without gas accumulating in the reactor. Any higher is beyond the point where it gets completely dissolved in water.

Controller was calibrated to the probe with 2 point calibration, pH 7 and 10 solutions.
 
au01st;559237 wrote: I saw noticeable on/off periods with my CA reactor setup, though I only ran it for a short while. I could sit on the couch and watch the pH climb to 6.72, hear the solenoid click, watch the pH drop to about 6.65, the solenoid clicks off, and the pH drops to 6.62 before starting to climb again. The whole cycle took about 30min at 1 bubble per 2 seconds, and dripping the effluent about 30ml/min.

Before I added this new probe, I could look at the controller a few times over the course of the day and I would see it in operation a couple times, and off a couple times. Nearly always on now.

Notable changes in the system:

1. I went from a 210/100 gallon tank system to a 300/150 gallon tank system with the same equipment, so system volume has increased significantly while the reactor is the same, except for the addition of the second media reactor in line after the GEO.

2. I said before, my acropora colonies have grown a good bit, so I think KH depletion thru the coral's growth has also significantly increased. I have a couple tabling acros the size of dinner plates now.
 
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