I hate ORP!

Randy Holmes-Farley

Reef Chemist
Premium Member
It is just not a reliable indicator except for gross overdose of ozone, IMO. The probe has a memory of what it has been exposed to in the past, and even with proper calibration, it may still depend on the probe history (presumably impacting organics and inorganics bound to the platinum itself).

For example:

My tank (with O3) was running in the low 300 mv, say 300-330 mv, depending on the pH and whether I freshly cleaned the skimmer or not. Calibration of the ORP with a commercial 400 mV fluid always showed about 410 mv, close enough.

I use the ORP probe for a couple of days to measure the ORP in the ozone reactor effluent (683 mV).

Then when I put it back in the reef system, it never gets above 276 mV for a week. What changed?

The I put it into the 400 mV calibration fluid. Still about 410 mV.

But on returning it to the tank, the reported ORP began to rise. After 15 min it was up to 288 mV. After 24 h, it was up to 305 mV.

So my conclusion is that both the 400 mV ORP callibration fluid and the high ORP exposure alter the probe in ways that are not corrected by simply allowing the probe to continue to sit in the system being tested.

In other words, ORP measurements do seem to matter what has been done to the probe before it was put into the test fluid, EVEN IF it still shows proper calibration.
 
Going from memory Randy and yes it go's back a while, I seem to remember the same issue's. I don't want you going on a wild goose chase, but look at were you place the probe and electrical wires that may cross the probes, this includes lighting, pumps and powerheads. The ORP probes wires are suppose to be shielded, but going back I'm remebering the same issue along the lines your mentioning. I could be completely off it's been a while.
 
Thanks for the suggestion. I tried moving the probe and wires, but that didn't seem to matter. It is in my sump, about 8 feet from the nearest mh ballast. :)
 
Maybe the high ozone and the 400 calibration solution had a cleaning effect on the probe similar to givng it a vinegar soak. Mine will drop depending on how long it's been between cleanings but even after a few days I'll get a drop of 30ish which it does seem to last a couple days. Is that the correct orp and when it comes back up the 30ish is it getting dirty? But if I don't clean it weekly it seems to rise even though by eye it is perfectly clean. Very touchy. It seems they have an optimum reading time starting at a few days and only lasting to about the 1 week or so. Very small window. The only good thing is that they drift up instead of down which helps to not O.D. the tank on ozone.

I bought a used Sanders which has a broken test tube top so I'm ordering a new corona unit from sanders that I'm going through the email tag game with Sanders to get. As slow as the interaction is for this part your articles may be published and it may go back to eBay!

If you want any graphs from controllers which show obvious cleaning times and rebound times for your article LMK.
 
you can always turn to the 24 hour taste test to see if the water is good or bad :lol: . I hate ph meters fwiw, actually anything electronic! Just wait 100 years for the next generation of meters :)
 
Randy, I feel your pain :D

This ozone thing has been driving me nuts for months now. I was at 287mv this morning and my tank is so clear you cant tell there is water in it. I just don't get it. The probe has to be reading something because when I feed, the ORP drops about 10mv for a couple of hours then goes back up. When I do a 20% water change, the ORP drops around 50mv then goes back up. Just cant seem to get it to stay consistently above 300.

Are you thinking of running your ozone through the skimmer instead of the reactor. I'm wondering in your case if it will make a difference.

FWIW, I tried a little experiment. I hooked the output of the generator to a 6 inch long air stone and laid it in the bottom of the first compartment of my sump. ORP actually dropped. It seems to work best when its hooked up to my skimmer.
 
Are you thinking of running your ozone through the skimmer instead of the reactor. I'm wondering in your case if it will make a difference.

I did, and it didn't. The ORP did not rise further, even without any GAC on the outflow. All it did was make my basement smell of O3.

I was at 287mv this morning and my tank is so clear you cant tell there is water in it. I just don't get it.

Time to declare victory, and move on to worrying about something else. :D
 
<a href=showthread.php?s=&postid=6942976#post6942976 target=_blank>Originally posted</a> by Randy Holmes-Farley
Time to declare victory, and move on to worrying about something else. :D



:lol:
 
See Randy I told you ORP was a nasty but cool subject and would pop your cork :lol:


Dr

It seems they have an optimum reading time starting at a few days and only lasting to about the 1 week or so. Very small window. The only good thing is that they drift up instead of down which helps to not O.D. the tank on ozone.

I agree 100 %. It always takes a few days for the probe to break in no mattter where it has been. I never used a calibration solution so can not speak on that issue. All I had was the quinhydrone test
 
<a href=showthread.php?s=&postid=1947452#post1947452 target=_blank>Originally posted</a> by Habib
ORP electrodes are subjected to coating and abrasion
by ORP measurement. The following is a procedure
for testing electrode(s) in solutions of standard
potential which will determine response or
maintenance requirements.

The procedure is give here: http://www.iqinstruments.com/ph/pdf/orp.pdf

That is a post from 2003... unfortunately the link no longer works.

I found that post because I recalled we did discuss the coating of the electrode by the ambient "soup". I know there should be more posts but I can't recall which words I used so it is not easy to find them back.
 
I have been playing around with ORP and the controller I designed for the last six months. From what I have found it is better at measuring reactivity trends and terrible at giving a good absolute reading. If that makes sense.

My approach in running Ozone is to measure the tank for a week get a decent baseline then then add 30 or 40 to it as your ozone setpoint. Let it run for a little while and see how things look.

My tank's ORP runs around 300 - 340, without ozone. When I was running ozone I controlled the reactor at 380. I did this for a few weeks until one day I noticed my feather dusters got stressed and lost their tails. So I stopped. They must be sensitive to the ozone. I did run ALOT carbon. ORP never did exceed 400.


You also see a good inverse relationship between ORP and Tank PH.
 
I have been having problems believing in my now-replaced ozone controller.

I just took the old probe off and replaced it with a brand new one, still with the preservative bottle attached to the end. Funny thing is, the orp didn't change at all when I hooked up the new probe. The unit itself is a replacement due to a failed prior one, and only a couple of weeks old.

The tank looks great, but I hate adding something blindly to the tank.

Overall, I've found this to be one of the most frustrating pieces of equipment...well, next to the skimmer with the same name!
 
<a href=showthread.php?s=&postid=6981193#post6981193 target=_blank>Originally posted</a> by Ixthys
Overall, I've found this to be one of the most frustrating pieces of equipment...well, next to the skimmer with the same name!

Let me guess............ Red Sea :lol:

Welcome to the club :D
 
When I first got my Red Sea ozonizer/probe it read REALLY low <200 and even lower on freshly mixed sw. I called Red Sea and they said to wash the probe with soapy water. Which I did and it didn't help at all.

It took at least a week to start giving readings that made sense. And everytime I cleaned the probe it would read low for a day or two.

Eventually, I quit using ozone as I didn't find it to be doing much for me but I kept monitoring the ORP. I noticed that only a 5% water change per week kept my ORP around 400mv. So now I don't use ozone or monitor the ORP. Just do my little weekly water changes and all is well.

Sooooo...that probably doesn't help the discussion at all LOL. Just my experience.
 
If you are reading 400 w/o ozone it's dirty. Soak in vinegar for about 1/2 each week to get a correct reading. The reason it didn't read correct at first was that it takes 1-2 weeks for it to initially "break in".
 
Hey Doc, Happy Saturday. :)

Well I don't usually do this but..................

The Red Sea unit w/controller is junk, IMO. Plain and simple.

You know you get what you pay for in this hobby. Most people buy this unit because it's an all-in-one and, supposedly, easier on the aquarist. Well, I got what I paid for and I will not buy or recommend this unit again.

I've seen all the threads on how people have this unit and they are very happy with it. Well I'm not. I believe at this point that the probe they use is inferior to say the Milwaukee or the Pinpoint. And I believe that the generator itself is inferior to say a Sanders or Aquamedic.

I have no scientific facts based on these opinions but I can read.
I have read nearly every ozone thread on this forum, and I draw my own conclusions.

Now I don't believe everything I read, but I think I can pretty much read through the BS.

After all, opinions are like............. well you know :D
 
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