We'll go over calibrating your ORP probe in our tenth episode of the Neptune Apex series. Let's begin with a quote directly from the Neptune Apex manual: "It is not necessary to calibrate the ORP on your Apex controller." Honestly, calibrating your ORP probe is a waste of your time and money in nearly every case. The calibration solutions usually cost more than the probe itself, and it's easier to mess things up than make it better. Unlike pH, knowing a precise number doesn't really tell you anything with ORP. We're really monitoring ranges, trends and large variances from those trends. Generally speaking, people monitor ORP for two reasons: 1. To control their ozone generator 2. To set off alarms if the ORP were to fall out of normal ranges For instance, a large downward swing could indicate a substantial drop in oxidizers because something large died in the tank. If at the end of the day, you still want to calibrate your ORP probe on the Apex, here is the first thing you need to know: ORP 400 solutions that are inexpensive and readily available cannot be used for this process. Step 1: You will need some pH four and seven solution as well as quinhydrone powder (it's the latter that is hard to find in small, affordable quantities). Step 2: Mix the quinhydrone into small amounts of four and seven pH solutions until it no longer dissolves, you can't really put too much in. Step 3: Go to set up menu, select ORP set up, then ORP calibration. It will say quin 7 settling. Step 4: Swirl the probe around in the solution a few times and wait for the settling number to stop changing. Once it has stopped for 10-20 seconds, hit OK. Step 5: It will now say quin 4; slide the probe in, swirl it around and wait for the settling number to stabilize for 20 seconds. Once it stops changing for 10-20 seconds, hit OK and you are done. I'm sure there are some legit needs to calibrate your ORP probe, so let us know in the comments section! Check out the entire Apex line: http://brs.li/neptuneapex Watch the whole playlist: https://www.youtube.com/playlist?list=PLBaMLrfToJyz8091y-PoECoUo5QfMGg1S Connect with us on Facebook: http://www.facebook.com/BulkReefSupply Check out our pics on Instagram: http://instagram.com/bulkreefsupply