Sudden ORP spike and stayed elevated

[Makara23]

I don’t care much about the actual ORP values, I only monitor ORP to see sudden drops or spikes. Something caused it to spike almost 100mV in a couple hours and it stayed elevated, and it wasn’t due to feeding cycle, pump on/off, or light cycles. It has been stable for months around ~360mV (ever since tank started).

Normally a sudden drop could mean something has died, but what does a spike mean? What are some plausible causes, should I be concerned, and should I take any action? Everything in the tank seems normal.

 

[Randy Holmes-Farley Verified Community Expert]

If a spike is not from a high or low ORP additive, then it is generally electrical interference or a change in the calibration.

I'd suggest cleaning it gently. Algae on it can raise ORP.

 

[Makara23]

If a spike is not from a high or low ORP additive, then it is generally electrical interference or a change in the calibration.

I'd suggest cleaning it gently. Algae on it can raise ORP.

That's correct, nothing new was added or removed.

By electrical interference, do you mean something in that tank could have possibly short-circuit?

Probe is not in the most accessible placement but I'll remove it and try giving it a gentle clean.

 

[Randy Holmes-Farley Verified Community Expert]

That's correct, nothing new was added or removed.

By electrical interference, do you mean something in that tank could have possibly short-circuit?

Probe is not in the most accessible placement but I'll remove it and try giving it a gentle clean.

Interference can be from nearby electrical devices or cords:

https://www.reef2reef.com/threads/orp-spike-when-skimmer-off.965226/#post-11082184