High ORP without Ozone

[trevorhiller]

I have a question about ozone. I purchased a unit for my tank hoping to keep the water sparkly clear. When I had my GHL, my ORP was always quite low (<200). Now that I’ve switched to Apex it creeps up to over 400 on its own (no ozone). I’m not sure if it’s a difference with the probe or what the cause is.

I do dose a few drops of Fergon DIY Iron as well as a few drops of Lugols a week-but I don’t notice a dramatic difference after dosing these even though I believe it should theoretically elevate ORP). It seems to elevate gradually as the probes sits and gets a biofilm on it (see photo demonstrating drop after cleaning probe).

I noticed after scrubbing my probes off (part of monthly maintenance) it drops off to around 200-250 then begins climbing again.

I’ve been hesitant to actually setup the ozone permanently because if I program it for say ORP <400 then ON it’s never going to run if I don’t clean my probe. If I do clean my probe, it seems like it’s going to run in a long burst
immediately after brushing it off.

I’d love to hook it up and let Apex do its thing, but I’m not sure what the right approach is here. My main concern is overdosing it and hurting the animals so I’ve been gun shy about deploying it.

Any thoughts? Do the probes really need cleaned that often or should I just leave it be and see what level it settles at for a few months.

 

[TangerineSpeedo]

Following

 

[Pankney72]

Heyo, I'm not the Esteemed Holmes-Farley but I do have a laboratory background.

I can't say for certain because I don't know your tank or the exact device or how you clean your probe, but that sounds like an equipment issue to me. Drops that precipitous make me think you're getting probe build up of some kind (charge vs calcium?). Assuming you're cleaning the probe properly it probably needs to be cleaned more often or used less frequently. I would check with the instructions and manufacturer on proper use.

 

[Dan_P]

Heyo, I'm not the Esteemed Holmes-Farley but I do have a laboratory background.

I can't say for certain because I don't know your tank or the exact device or how you clean your probe, but that sounds like an equipment issue to me. Drops that precipitous make me think you're getting probe build up of some kind (charge vs calcium?). Assuming you're cleaning the probe properly it probably needs to be cleaned more often or used less frequently. I would check with the instructions and manufacturer on proper use.

Agreed. Could be an electrical issues, a response to another electrical device turning on or off at that time,

 

[trevorhiller]

The only other thing in that chamber is the skimmer. Dosing is done down stream so I don’t think that would be the issue.

to clean the probe I brush it off with a toothbrush and see this dramatic drop each time.

 

[Randy Holmes-Farley]

Algae growing on probes tends to raise ORP over time. If the probe is getting light on it, blocking that light may be helpful. In addition to a toothbrush, try soaking it in vinegar (say, 1 h) which should kill algae on it, since a toothbrush might leave a thin layer that regrows faster. We can see if that leads to a slower rise.

FWIW, Fergon (ferrous iron) should lower ORP, but Lugols will raise it.

I don't think it likely that the ORP is really around 400 mV without any oxidizers in use, but it isn't impossible.

 

[piranhaman00]

The simple solution is to unplug the ORP probe, it means nothing.

 

[trevorhiller]

Algae growing on probes tends to raise ORP over time. If the probe is getting light on it, blocking that light may be helpful. In addition to a toothbrush, try soaking it in vinegar (say, 1 h) which should kill algae on it, since a toothbrush might leave a thin layer that regrows faster. We can see if that leads to a slower rise.

FWIW, Fergon (ferrous iron) should lower ORP, but Lugols will raise it.

I don't think it likely that the ORP is really around 400 mV without any oxidizers in use, but it isn't impossible.

There is a light in the sump, but it is indirect to the probe location. I'll try the vinegar soak and see if helps. It really does seem like I am scraping off a film with the toothbrush dramatically altering the reading although nothing visible comes off.

I might have to fashion some sort of light blocker if that's the case.

 

[trevorhiller]

The simple solution is to unplug the ORP probe, it means nothing.

So you recommend just running ozone regardless? For what duration?

 

[Tuan’s Reef]

Do have still have the GHL unit to compare?

 

[trevorhiller]

Do have still have the GHL unit to compare?

Unfortunately no

 

[Randy Holmes-Farley]

So you recommend just running ozone regardless? For what duration?

FWIW, this is from an article of mine (second one):

Ozone and the Reef Aquarium, Part 1: Chemistry and Biochemistry by Randy Holmes-Farley - Reefkeeping.com

Ozone and the Reef Aquarium, Part 2: Equipment and Safety by Randy Holmes-Farley - Reefkeeping.com

Ozone and the Reef Aquarium, Part 3: Changes in a Reef Aquarium upon Initiating Ozone by Randy Holmes-Farley - Reefkeeping.com

Here are my recommendations for ORP monitoring and ozone control in reef aquaria using a properly sized ozone generator that appears to be working, and a properly calibrated ORP meter:

1. If the ORP never seems to rise above 375 mV after initiating ozone, do not worry about controlling the ozone or the ORP. Just let it run full out. Also, do not worry about needing a larger generator, assuming it has driven up the ORP by at least 25 mV above where it was before adding ozone. It is likely accomplishing the necessary tasks (such as making the water clearer). Only if some other aspect of ozone use is unsatisfying (e.g., lack of water clarity) would I look for other options such as a larger ozone generator or a better contact chamber.

2. If the ORP starts above 375 mV, or rises there during ozone use, using an ORP controller would be valuable to prevent the ORP from rising too high. Use the controller to shut off the ozone when the ORP rises too high. Another option would be to shut off the air flow to save the dryer's media, but be sure that water cannot flow back into the ozone generator if the air stops. I would set the ORP target somewhat above the baseline ORP in the absence of ozone - at least 350 mV, maybe 400 mV, but never above 450 mV.