ORP Question

Js.Aqua.Project · Mar 13, 2018

Ok, so even though I have read RHF's Reef Keeping article at least a dozen time over the last year, I still am occasionally unsure of what to do with ORP readings.

For example, my Apex is currently sending me alerts that my ORP < 300, this started 3 days ago.

A while back, for a couple days, I was getting alerts my ORP was > 450.

What should I actually do with this knowledge?

A visual inspection of the tank does not reveal anything abnormal.

I don't dose ozone or any pH buffers, just Ca, dKH, and NoPox.

Rest of tank parameters: (not that they directly correlate)
SG 1.025
Ca 450
dKH 11.2
Mg 1350
NO3 2
PO4 .08

Randy Holmes-Farley · Mar 14, 2018

Assuming you are not dosing oxidizing chemicals like ozone, then ORP never gets too high in a reef tank and there is never any cause to try to lower it. Whether the 450 mV is real or not, doesn't matter.

ORP does cycle through the day and will be impacted by water changes and chemical additives, but to get both high and low warnings on the same system a few days apart is unusual, but might just be testing error.

In a low ORP alarm, I'd check the tank over to make sure there's no dead fish floating around, but other than that, I'd probably do nothing special.

Js.Aqua.Project · Mar 14, 2018

Thanks, I am going to lean towards a probe error.

Js.Aqua.Project · Mar 14, 2018

Thanks, I am going to lean towards a probe error. The tank itself has seemed fine through all the errors.

At what levels would you say it is actually needed to take corrective action for ORP?

Randy Holmes-Farley · Mar 15, 2018

Unless you are using an oxidizer like ozone, I not sure a high ORP alarm is useful. I'm not sure what one would do other than recalibrate the probe. I don't think it gets too high without oxidizers, although it might tell you if you are dosing an oxidizer and didn't realize it.

At the low end, I might set it for 50 or so mV below where the tank normally reads at its lowest, to see if it can help detect a problem like a big dead organism before you might see it.