ORP rising without ozone

[jaaash]

Hi all, I have an established 65 gallon that has been going on for 2-3 years now. It is doing very well. In the last few months I started Ozone and raising my ORP. I like experimenting, it does seem to clear up the water and the corals have appeared to respond to the cleaner tank water. Up until this week, it has mostly been on. It fluctuates between 350-380, turns on and off when it hits those numbers. It would go down below 350 when I feed the tank, or do a water change, then come right back up.

The issue now is all of a sudden this week it seems to be going up on its own. Ozone is off, and it was rising above 400. I did a water change, it dropped down to 330, then held steady and now is rising again back to 360 today.

Anyone understand the use of orp that can help me here? Is it the probe? Is it because I had an already established tank that it took a few months to get to this point?

No UV, No carbon. Just a doc skimmer and reefmat for the filter with sponges.

 

[mmorrison55]

Im seeing the same thing. I can turn off my ozone generator do a water change, and the ORP will drop to ~300 but then a week later it’s reporting over 400.

I also dose kalkwasser, but I wasn’t aware that Kalk could raise orp, so idk what the culprit is unless it’s just residual ozone.

Are you using the apex and orp probe to test your ORP level?

Maybe Randy Holmes Farley will see this and have a theory.

@Randy Holmes-Farley

 

[jaaash]

I do use apex and orp monitor. I did just purchase a different device and orp probe. I will install tomorrow to test if it matches. I dose too but I dont think that has anything to do with it.

 

[jaaash]

Okay I think it is the probe. My other orp probe is showing what I would expect when the ozone is off at 200 and dropping.

 

[mmorrison55]

Interesting, it may be time for a new orp probe myself.

I pretty much ignored the orp reading. I had it set to alarm me if it was excessively high since I do use ozone, but when you start seeing it in the mid 400’s when you th8nk it should be in the 2-300,you do get concerned.

 

[Randy Holmes-Farley]

An ORP probe growing algae can see rising values.

FWIW, ORP never gets too high without adding oxidizers such as ozone, no matter what a probe reads. :)

 

[mmorrison55]

I pretty much ignored the orp reading. I had it set to alarm me if it was excessively high since I do use ozone, but when you start seeing it in the mid 400’s when you th8nk it should be in the 2-300,you do get concerned.

An ORP probe growing algae can see rising values.

FWIW, ORP never gets too high without adding oxidizers such as ozone, no matter what a probe reads. :)

and if you removed the oxidizer via a water change, and didn’t turn ozone back on, after said water change,can orp rise in that scenario?

Im thinking like jaaash commented that it’s the orp probe itself if orp is rising after a water change and no ozone has been added after the water change.

 

[Randy Holmes-Farley]

No, any ORP rise from ozone is completed in less than a day.

 

[Randy Holmes-Farley]

Water changes usually drop orp due to the use of trace elements in a low ORP form, such as ferrous iron. It is more soluble so would be the first of choice. Over time after the change, those low ORP forms may be converted to higher ORP forms (or removed) and hence ORP rises.