View Full Version : ORP of 530

11/02/2005, 04:27 AM
Hi Curt,

I bought an ORP probe from you at MACNA for my Aqua Controller II. The AC II is about 1 year old now, as you replaced the innards when it was ruined due to being flooded by the previous tank owner.

The probe is in my sump, and the tank and sump have a ground probe. ORP is very high, but I don't run ozone. What do you recommend?

11/02/2005, 11:21 AM
Here are some things to try:
Clean the probe with a soft-bristled toothbrush. Sometimes a biofilm will develop around the probe and result in high readings.
Unplug serial cable and see if the readings change. Maybe a ground loop. If so install an isolator (part # SERIPC9).
Make sure that pH compensation is off for the ORP probe. The industry norm is off, and having it one will raise your ORP by about 100 mV.


11/03/2005, 05:57 PM
what should it read my says around 425 to 450 all the time. my probe is also new about 3 months old!:rolleyes: :rolleyes:

11/03/2005, 06:19 PM
This probe is about a month old now, and it clean. I just used a soft toothbrush as directed and knocked out some tiny baby brittle starfish. The reading went to 425 but within a minute rose up to 432. I'll see what it reads tomorrow.

I don't have a serial cable plugged into my AC II.

I was told the temperature probe acted as a ground as well?

I'll have to check the setting for pH compensation. Would that be in the ORP menu or the pH menu?

11/03/2005, 06:26 PM
Readings in the 400s are not uncommon. Most tanks run between 300-400 but well skimmed/maintained tanks do have ORPs that go over 400. I recommend that you read Randy Holmes article on ORP if you haven't already http://reefkeeping.com/issues/2003-12/rhf/feature/index.php.

pH compensation is in the ORP menu. It is only on the Pro units that the temp. probe is a ground reference.


11/03/2005, 10:07 PM
Okay, I'll have to check that menu then. Current ORP now is 513.

11/03/2005, 10:09 PM
Done. Now it reads 444. Remember, I don't run ozone, and to be honest I think the water quality looks really nice (clear, no discoloration). So is this number believable?

And when it comes time to calibrate, what ORP solution am I seeking?

Do you still think I need that ground loop you mentioned earlier?

Thank you for taking the time to answer my questions.

11/04/2005, 03:33 PM
ok thanks i will read randy's article!

11/04/2005, 03:45 PM
That ORP is believable. I have heard of others with that high of a reading, and my personal tank had a similar reading when it was in its peak condition.
Use Quinhydrone, and pH 4.0 and 7.0 pH calibration to make the ORP calibration solution. The procedure is discribed in the manual.
If you have serial cable permanently connected to your PC then we recommend the isolator for the AC2. Otherwise you don't need it.


11/04/2005, 05:00 PM
Thanks. I'll have to get my manual out and read that section. I was told that if I run ozone, it should turn off after ORP is 375. So having it at 458 (as it is right now) it seems like ozone wouldn't be a good option for my setup.

11/05/2005, 11:47 PM
It appears that water quality is quite good in your tank, and doesn't require ozone. The only reason I'd run ozone on a reef tank is to make the water crystal clear and get yellow out.


11/06/2005, 01:32 AM
Thanks. Since ORP has never been a factor, I really didn't have a guideline to follow.