Constantly rising ORP

Husker · Aug 10, 2017

I have read Randy's ORP article, but I was just curious if anyone can explain this ORP curve. The levels have been daily rising the past few weeks and now they have perhaps plateaued. Nothing seems wrong with the tank, this is more of an intellectual problem than a practical one.

Monkeynaut · Aug 10, 2017

Interesting. I am waiting to see where my tank goes with a different salt mix. Mine dod the same thing though when I used HW reefer

Achilles · Aug 10, 2017

Good question, ORP can be kind of tricky to understand, just knowing a few things about it Will help you understand the concept. Firstly ORP probes have a weeks break in period when you first start using them. Secondly ORP has a direct relationship with your pH , So if you cross reference your pH and ORP and you will see that relationship on the Apex graph . Now what does ORP read? for simple terms how clean is your water more of a complex understanding of it it tells you how much potential there is the breakdown nutrients in your tank at any given time. Third part to understand ORP there is no particular number to shoot for and you will often see a range of 200 points a day not to be alarmed like I said before it has a relationship with your pH so it rises and falls through the day and night . So for example if you ORP is trending high your water is cleaner and has more potential to break down nutrients, when your ORP is treading lower.
If you need anything else I can always point you in the right direction of a few articles that would go more in depth.

Achilles · Aug 10, 2017

And if I'm mistaken, please correct me randy homes I would love to learn more about this subject ![emoji4]

Husker · Aug 10, 2017

Thank you. I have read Randy's article on the subject and have a general understanding of redox and the relevance of the measurement. I wasn't aware (or forgot) that the sensor needs a few weeks to calibrate. This is on a new system, so that very well could be the case.

Monkeynaut · Aug 10, 2017

Does it take weeks? I thought a week would do.

Husker · Aug 10, 2017

Mine has been rising since July 14th, although the rate of increase has decreased the last couple weeks.

Achilles · Aug 10, 2017

Well from what I recall Paul from Neptune telling me is that it should take one to two weeks.in order for it to start becoming accurate.

Husker · Aug 10, 2017

That seems accurate. For the first week or so there was a lot of bouncing around. Now it seems to be just rising continuously.

It isn't pH. My pH is pretty low, around 7.6-7.9, but I don't dose anything yet because of no alk consumption and the tank is in a basement. It fluctuates a bit through the day, but not a ton.

Any other interesting ideas?

Maacc · Aug 10, 2017

My ORP probe did almost the exact same thing when I added it.

Achilles · Aug 10, 2017

Husker said:
That seems accurate. For the first week or so there was a lot of bouncing around. Now it seems to be just rising continuously.

It isn't pH. My pH is pretty low, around 7.6-7.9, but I don't dose anything yet because of no alk consumption and the tank is in a basement. It fluctuates a bit through the day, but not a ton.

Any other interesting ideas?

That weird I've never seen my PH drop that low, maybe your ph probe needs to be recalibrate. Also ph has more to do with light and algae ( micro or macro) growing and consuming CO2 and Producing O2 which in relation brings the Ph up.

Husker · Aug 12, 2017

Yah, I understand the dynamics of pH in aquaria. I'm not too worried about it, and the numbers seem reasonably expected for a basement tank that doesn't dose and is in a locked down A/C'd house. I got into troubles with past tanks for chasing numbers when there weren't any problems, so I am doing my best to avoid the same mistakes. [emoji1]

By the way, the ORP is still rising [emoji848]...

CNDReef · Aug 12, 2017

Do you have anything in the tank that's getting fed/ creating waste?
Maybe the Orp keeps rising if there's nothing making a mess of the water. ( not sure if when you said new system, you meant tank )

Husker · Aug 12, 2017

I have a kole tang, a C. solorensis wrasse, A. occelaris clown, 2 Psuedoanthias dispar, and a coral beauty angel in a 150 gallon display + 55 gallon display refugium + 75 gallon sump. I wonder if if it could be a function of the macroalgae/seagrass?

Husker · Aug 20, 2017

So here is an update in case anyone has the same situation. The ORP peaked and is stabilized. Now little drops correspond with my feedings. I think it may have been my tank maturing more than the probe settling in.

Randy Holmes-Farley · Aug 20, 2017

Thanks for the update.

Happy Reefing.

XNavyDiver · Aug 20, 2017

Well, I don't pretend to know what your average of 470 orp means other than your water has more oxidizers than reducers? I don't know the significance of these numbers. All I know is when my orp is trending downward, my pH trends upwards.

Randy Holmes-Farley · Aug 20, 2017

XNavyDiver said:
Well, I don't pretend to know what your average of 470 orp means other than your water has more oxidizers than reducers? I don't know the significance of these numbers. All I know is when my orp is trending downward, my pH trends upwards.

That's normal, and relates to the fact that some redox reactions that go into determining ORP involve H+, so changes in the pH (in the H+ concentration) impact the apparent ORP:

ORP and the Reef Aquarium - Reefkeeping.com
http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm

example from it:

O2 + 4H+ + 4e- <--> 2H2O

In this reaction, H+ does participate. Consequently, the oxidizing power is related to pH. As H+ is raised (by lowering pH), the reaction is driven to the right. One way to think of this is by LeChatlier's Principle where increasing the concentration of one species drives the reaction to the other side. In this case, lowering the pH increases the oxidizing power of the oxygen, and consequently raises the ORP.

Husker · Aug 20, 2017

I have the same trends. But my ORP was rising for several weeks independent of pH. Admittedly, my pH is pretty low. I am not dosing much for Alk yet and the tank is in the basement of a heavily AC'd house. The probe calibration may be a bit off, too, but that is kind of a different topic.