ORP slow drift

[Tangdora]

Hi

Looking to get a bit more insight into ORP. About two week ago I cleaned and calibrated my 4 Neptune probes. Prior to the cleaning my reading ORP reading was hovering between 420 and 450. After cleaning it dropped to around 250 - 270 but over the last two week has been drifting back up towards 400 ( today it hit 360). The part I’m confused about is out of a curiosity sake I ordered a pinpoint 400 calibration solution a few days earlier just so that could see how off my reading are which turn out to be about 38 mv. I know the actual orp number does not mean much but would stood out is the probe responded instantly to the solution in seconds. Yet in tank water the value never seems to return to pre cleaning level after a minute or two and seems to take days to get drift back to pre clean level. Curious as to why this is the case.

 

[Randy Holmes-Farley Verified Community Expert]

Various things will cause drift, including algae or bacteria growing on it, and stuff binding to it. It can also take a significant period of time to acclimate to the water.

An ORP calibration fluid is far more strongly buffered in ORP than is the tank water. So it stays steadier in the fluid.

 

[Ryan - Serious Reefs]

In my experience, we test ORP mainly because we can, not because it's particularly valuable or actionable. The only real exception is using it as a safety control for ozone.

That said, if ORP drops dramatically, I'd closely inspect the tank or look for a major casualty, like a large fish that recently died. In your case it is probably something related to cleaning/calibrating it.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, I measured it for years, never once did anything because of it, and then just stopped bothering to measure it. :)

 

[Tangdora]

FWIW, I measured it for years, never once did anything because of it, and then just stopped bothering to measure it. :)

Yes I only use it to detect abnormal spikes or dips as well was just curious why it increases so slow back to previous level in tank water when it changed so quick in the pinpoint solution. But you explanation summed it up thanks again.