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Life of a pH probe in a Ca reactor


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I'm curious how long the average pH probe lasts in a calcium reactor. I have a Milwaukee pH controller that I bought used a year ago and I've noticed that it drifts fairly rapidly and I usually recalibrate it monthly. I know pH probes should be recalibrated every day, but I feel like it drifts further than it should. Then this morning I woke up to my Ca reactor full of CO2 bubbles, cloudy with dissolved calcium carbonate, and the pH probe was reading 7.1. I'm pretty sure the pH probe needs to be replaced now, but wanted to see if anyone else has had a similar issue.

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Been running the same probe for the last 3 years. It drifts at a roughly the same average rate as my newer probe so I still use it. 6 month calibrations usually keep both in line.

I used to run water parameter monitoring equipment at a job site in North Hollywood. The pH probe was in-line and had pretty caustic 5.0 pH water running through it at all times. The probe membranes would still last about 1 year before I had to replace the membranes on the pH probes.

Yours sounds like a dud and hopefully it didn't nuke your tank. Did you not have another pH probe in the main display tank to tell you the pH is lower than it should be? I would imagine your DT pH got really low during this episode.

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+1 on an additional pH probe in the tank. If my Apex sees a pH spike in the display tank it shuts down the CO2 supply until pH normalizes, protecting the corals from not only the pH swing but the associated Alk and Ca spikes.

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No unfortunately I haven't added an in-tank pH probe to my system yet. I have no clue what the alk level is or pH is now, I was running out the door when I noticed it this morning. I imagine I'll have some damage this evening on my SPS, but if they haven't died yet from a dip to 82 ppb, who knows! I think I'll replace the probe and hope for the best.

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Get that Apex already Gig em! You travel way too much sir to not have everything automated! At least it comes with one pH probe already so just throw the money you were going to purchase a new probe and put it into a full Apex system. :-)

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I've been trying all morning to figure out whats wrong with my calcium reactor and I ran the pH probe through the typical 4.0, 10.0, and 7.0 pH calibration solutions and the probe continuously reported about 0.6 high on all three points. I then just unplugged the pH probe from my Milwaukee MC-122 controller and noticed that without a probe connected it was reading ~2.9-3.1. I'm not sure if no signal would create a reading this high, or if maybe my Milwaukee controller is to blame by biasing all pH readings several degrees high. I can't find anything online right now about what the controller will read without a probe plugged in, but maybe someone on here also has a Milwaukee and can see what happens when the probe is unplugged?

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Just as an update, I purchased a lab grade pH probe from BRS and replaced my old probe. The pH in my Ca reactor according to my old probe when I changed it was 7.3 and after calibrating the new probe and placing it in the reactor it read 7.1.

I still believe there was an issue with the old probe because it was impossible to calibrate it on the 4.0/10.0 calibration points becuase they would never agree. I believe there was probably a span offset in either the high or low range on that probe causing it to be impossible to accurately calibrate it there.

The odd thing about this situation though is that if my pH truly has been sitting at 7.1 this whole time, then the question is why has my alk risen from 82 ppm to 136 ppm in a matter of a week? When my old probe first starting creating issues it had a high bias and left the CO2 running longer than it should have coupled with a clogged output line on the reactor causing no turnover in the reactor. Over about a week or two a good inch of media dissolved and I ended up shutting down the reactor, draining it, and cleaning the lines before starting it back up again.

JeeperTy and I have a current theory that the alk continues to rise due to left over small particulates that have been trapped within the media from the massive dissolved event. If I had rinsed the media after draining it, this probably would not have happened. I'm just going to run the reactor without any CO2 for a while until the alk levels begin to drop again and I will turn the CO2 back on.

Just thought this may be a good lesson learned for anyone else with a Ca reactor who may face a similar situation in the future.

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You forgot to mention my other theory... that you were a bad scientist! [emoji24] Bwahahaha!

It is quite baffling to have that much of a rise in alk with basically a neutral solution like you said. We might not ever know but your plan forward seems solid.

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Says the man who left the scientific industry!

You forgot to mention my other theory... that you were a bad scientist! [emoji24] Bwahahaha!

It is quite baffling to have that much of a rise in alk with basically a neutral solution like you said. We might not ever know but your plan forward seems solid.

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