redox issue (P3ex but also did it on P2ex)

basically my redox is alwasy in the region of 400+/- 20 - have calibrated 2-3 times with the 220mv solution and all is ok for 2-4 hours then the redox raises up to the high readings!

it all worked fine on my last tank set-up but on my new build i fitted the redox probe up in the weir as this is the furthest place away from my ozone input (going through deltec apf600)

thought it might be that i had my pc connected to the unit via usb all the time, disconnected and re-calibrated but high readings still come back

surely my water cant be that high in redox as it would read that not long after leaving the calibartion solutions?

any ideas?

just answered this in the German section ...

if you cleaned the redox probe you may removed the oxide film
this film recovers in some weeks, during this the readings are raising

-> wait until readings stabilized, do some calibrations frequently, avoid damaging the film on the electrode (don't clean this area)

if nothing helps - maybe the probe is not working correctly anymore (lifetime 0.5 - 2 years)

one thing i forgot to mention, is i have a storm stick, and 4 dimm ballasts over the top of the tank!

now if it is a film issue, how do u say to calibrate the probe with the 220mv solution? swill it around in ro, then carry ou the null and put the probe in to the solution, then swill in ro again, then put back in tank??

if that lifetime of this probe could be at min 1/2 a year thats a bit poor isnt it!? well if this is the case the uk rep will be getting a warranty claim as i have not had it that long! but im also getting not much support here!

I think you need to understand Redox probes and ozone

By the sounds of it you are using ozone so having a redox reading above 400 is very normal, if you did not want this then stop using ozone it is that simple. Ozone will raise the redox potential of your tank way above 400 if left un checked, thats the purpose of controlling it with a redox probe

There is nothing wrong with your probe

1. does it calibrate - yes
2. Does it repsond quickly to the tank ORP after calobrating - Yes
3. 400mV reading in tank injected with ozone - VERY normal and the reason you are using ozone

Result - perfect probe.

When you clean or calibrate a redox probe you remove the ionic field that a redox probe uses to read accurately and a sign of a good probe is how quickly it rebounds back to reading correctly

Your probe based on what you have said is perfect.