ORP - is there a "normal" level?

[JT101]

What is considered "normal" ORP? My tank (prior to replacing my Coralife 65G skimmer with a Reef Octopus Diablo XP160) would hover around 450-490. Ever since the change, it's over 500, usually around 525-545. How could a skimmer increase ORP, and can it ever be TOO high? I know it can be too LOW, but isn't higher better....???

 

[Boomer]

There is no such thing in a reef tank of 450-550 mV JT, unless one is running heavy Ozone. A good running reef tank will be in the high 300's. Most are in the mid-300's. Fresly made seawater is ~ 275 mV or slightly less.

1. Most of the time it is your ORP probe with algae on it. Their O2 output at the algae probe interface will raise the ORP in that immediate area. Clean probe.

2. Bad probe.

3. Out of so called "calibration".

There are some tests that can be done for 2 & 3

High ORP, is not an issue, unless it raised high using oxidants like Ozone, Hydrogen peroxide, Potaasium permanganate, etc.

 

[JT101]

There is no such thing in a reef tank of 450-550 mV JT, unless one is running heavy Ozone. A good running reef tank will be in the high 300's. Most are in the mid-300's. Fresly made seawater is ~ 275 mV or slightly less.

1. Most of the time it is your ORP probe with algae on it. Their O2 output at the algae probe interface will raise the ORP in that immediate area. Clean probe.

2. Bad probe.

3. Out of so called "calibration".

There are some tests that can be done for 2 & 3

High ORP, is not an issue, unless it raised high using oxidants like Ozone, Hydrogen peroxide, Potaasium permanganate, etc.

Thanks Boomer, I'll check things in steps, but I bolded one thing you wrote above because it might be connected to the problem...

I just poked my head around in the sump. Guess where the tip of the ORP probe is? Right under the output of the skimmer! The water coming out of there is bubbly and, I assume, more oxygenated than the rest of the tank. I probably stuck it there when I installed the new skimmer (replaced my other Coralife 65G). I'll try moving the probe out of the bubbly stream and see if it changes. If not, I'll try cleaning it and then check calibration (I have cal fluids etc).

Thanks
John

 

[Boomer]

John, O2 levels have very little effect on ORP. It is really the some total of the oxidation reactions at the probe Algae interface, where O2 is often involved. I should have made it more clear. However, a ORP probe in a bubble environment is not a good thing for reliable readings.

 

[sig45]

I have noticed a similar reaction in my system. ORP is ~500. Usually runs in the 400s. I do not use ozone. Only heavy skimming in well fed tank. Probe is clean and relatively new. The corals 'look' better over 300 although I realize that this is not an established means of determining tank/system health.

Sig

 

[Boomer]

Sig

There is something wrong. You can not get those ORP levels that high without ozone or some other oxidant being added or a probe with Algae onit. Or are you saying you have put the probe some place else now and had the problem ?

 

[sig45]

Boomer
I checked probe and there was some debris jammed deep inside sheath. After cleaning im running around 340. Thanks for input.

Sig

 

[Boomer]

Ok, sounds more like it.

 

[Paul B]

Boomer, nice to see you. I have not heard from you in a long time. Hope you are well.
My ORP reads 383 but I never cleaned my probe and it is many years old. I also use ozone so it could be that high. I don't pay any attention to the reading, I just want to know it is working and I can remove the hose to smell it for that test.
Paul

 

[Boomer]

Hi Paul

Long time no see. All is well, I have been with Sanjay for the last 7 days.

That is because the probe is shot and locked into that 383. ORP or pH probes can't last for years, usually 2-3 years. After that you start getting drift, lock-in readings or can not cal properly.