Reef tank pH: When should I calibrate my pH probe for an aquarium pH monitor or controller? - BRStv Reef FAQs
Calibrating your pH probe is an inexpensive and fairly quick process and the general best practice is to check the probes against a 1$ packet of pH calibration solution on a regular basis. The exact frequency at which you perform the check can be determined based on the application.
During these probe checks, if you find the pH probe is not acceptably close to the standard solution, than the calibration process should be performed. If the probe is reading accurately, there is no need to calibrate and you can move on.
Both 7pH and 10pH calibration solution will work for reference, but 7pH solution is probably best for monthly checks because it is closer to the 8.0pH range most probes will be used to read. You could check against both 7pH and 10pH every time, but that may be a little redundant because the accuracy can easily identified using a single reference solution.
If using the probe to control equipment such as a calcium reactor, refugium light, CO2 scrubber or kalkwasser dosing, you should certainly check your probes monthly because the accuracy of the probe will have a direct impact on the equipment performance and health of your reef tank.
When using the pH probe to monitor your tank for no specific reason other than to indicate when something is catastrophically wrong, absolute accuracy is less of a concern and a quarterly check, every 3 months, should suffice. When pH strays so far out of range that life in the tank is potentially compromised, the pH probe should register the change, regardless of accuracy.
Recalibrate for the most critical pH related applications when the reading strays 5-7 hundreds of a pH point. For less critical applications, a tenth of a point is an acceptable variance.
Quality of your pH probe affects accuracy and how long it will last but the differences are not so visually obvious. Check out our video BRS Lab Grade Probes, What’s the difference? to learn about the internal differences and which probe to choose for your specific application.
For all of you Neptune Systems Apex users, check out our entire Controllers & Testing playlist to learn about calibrating your probes and a number of other helpful topics to hone in the monitoring of your tank.