ORP Calibration

[Yomeister66]

Does anybody know how to calibrate an ORP Probe? I'm using one on my ozone controller but I'm not sure if it's working right.

When I got it about 8 weeks ago, the ORP in my tank was in the mid 200s. Red Sea recommends 300-350. I raised it slowly until it read about 335. The unit shut off (presumably since the red light went off) but the ORP kept creeping up to the 360s. I shut the unit off completely and ran it for about an hour every week. During the week the ORP would drop to about 320, then I'd raise it to 350 and turn the system off.

The last 2-3 weeks, the ORP reads in the 360-370 range every time I turn it on, so I haven't been running any ozone at all. Heard some stories of people running their ozone at higher than recommended because the Red Sea probes are supposed to be reading high?

 

[mojoreef]

I run an Aquacontroller and thier is calibration fluid available for my orp probes so it might be worth a phone call to red sea to see if they have the same. If you have carbon at the output of the skimmer (assuming you rn it into the ozone into the skimmer) it should take up any residual ozone you may have.

On a side note my orp never goes below 425 weither I run ozone or not



MIke

 

[Boomer]

Yomie


It is fine to let it run up to 400 mV, try not to exceeded 425 mV. It also sounds like the unit is not shuttting off the ozonizer. Are you sure it is hooked up right ? A well run reef tank can approach the 400's, without ozone. Red Sea's recommnedation is a little on the low side, more like 350-400 mV. Cleaning the probe weekly is very important, as any algae growing on the probe will rasie the ORP.

Read this

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

Mojo

You have something wrong also. No such thing as a ORP of 425 without ozone

residual ozone

Also no such thing (99% of the time), it is bromine bleach you are/need to remove, as O3 oxidizes bromide to bromine. When ozone hits seawatewr it only lasts for a couple of seconds. If you had a salt with no bromide, such as some of the public aquarium salts, then yes there may be residual ozone. They use degassing towers to vent it out. A low range chlorine test kit, using the DPD Method, will let you know if there is either, as bromine, chlorine and ozone kits usually use the DPD Method.

 

[Yomeister66]

Thanks for the info guys. Did some more research and apparently these probes get dirty real easy. Took it out, soaked it in vinegar for 10 minutes, cleaned it with a soft tooothbrush (not my own) and returned it to the sump. ORP reading was back to 290. But I'll order some calibration fluid from Marine Depot as a back-up.

 

[mojoreef]

residual ozone

ROFL you know one would think after you have spanked me a quarter millions times for saying that I would wake up

You have something wrong also. No such thing as a ORP of 425 without ozone

Ok so now you have my attention. I run two ORP probes, Bought a second one because I couldnt believe the first (even after calibration). Both probes are with in 3 points of each other all the time and my orp never goes under 425 (ph compensated). Even if I take the ozone offline for a week it still stays thiers. I have drops in orp of around 20 points from time to time. Actually had a 50 point drop after treating for red bugs (it did drop below 425 then for about a week).
Steve Weise who has a fairly large tank also has the same high readings all the time to (a little higher actually). DO you think its from reading the water only 4 inches below the surface??


Mike

 

[Boomer]

I have heard those stories many times and do not buy them. Usually it is a probe/s problem. It may be a to near the surface thing. Bubbles to high a current, dirty probes etc. Ever time this comes up and I say clean probe, get some REAL calibration solution, it sure is re funny how I'm always right Go to that link and look at Simons readings take note his are where you are at. Later he decide to listen, clean probes etc (posted it on our chem forum). and guess what ? His ORP went into the 390's It is for sure we/you ca get higher readings then we did in the olden days, without ozone, buy you guys are saying higher than the ocean for the most part. I have had guys even argue 475 with no ozone, to the point where they get mad, as I don't buy it.


ORP Standards

Many ORP meters do not permit calibration, but some do, and for detailed ORP measurements, including situations where ORP is being controlled (such as when using ozone), it is worthwhile calibrating (or checking the proper operation of) the meter. Usually, the calibration is quite easy given commercial ORP standards. A variety of standards are available, including Zobell solution which can be obtained from Cole Parmer for $21. It is a solid that is reconstituted from deionized water, and has an ORP of 231 ± 10 mv. Another common standard ORP solution involves putting quinhydrone into pH 7 and 4 calibration solutions to make standards of 86 and 263 mv, respectively. A third standard is Light's solution, which uses the Fe++/Fe+++ reactions described above.

Do you have quinhydrone and or Zobell solution

Feel free to e-mail Mike Ross and tell him I sent you. I had him come to the chem forum under my name ( boy did the jokes fly around that week :lol to help Randy and Habib undersatnd ORP and ORP probes. What kind of ORP probe do you have ? You want a Platinum Band/Double Junction for seawater which is best. The one I gave to Randy was $250 ( 2 of them, the other was a HACH)

http://www.sensorex.com/products/orp_electrodes/ORP_sensor_products.html


Look at thease two threads

http://reefcentral.com/forums/showthread.php?s=&threadid=224186&highlight=mike+ross

Mike Ross Thread ( no comments Mojo)
http://reefcentral.com/forums/showt...4&perpage=25&highlight=mike ross&pagenumber=2
ORP staying there

At times some probes like to "lock" in to a ORP, same for pH probes and just stay there. I once had a guy tell me that their waste water pH was 6.8, never claned the probe or removed it for any reason......FOR TWO YEARS. I had him put it in a pH 10 buffer and it still read 6.8 :lol:

 

[mojoreef]

The probe sites about 4 inches into the water at the surface of the tank, no real big flow or bubbles in that location. I clean all my probes (except the one in the calcium reactor once a week. The probe I use is a Platinum Band/Double Junction called a lab grade. As for calibration, I have done it a few ways, one was by mixing quinhydrone into pH 7 and 4 calibration solutions. and then the other way was a premix over the counter solution.
One probe is pushing 8 months old and the other is only about 3 months old.

The probes are in a holder that keeps it with in 6 inches of both the ph and temp probes, this hold kind of creates a low flow area about 4 inches into the tank. When I just had one probe, and saw the orp in the 425-450 zone I did several calibrations but kept coming back to the same numbers, moved the probe to the sump and got slightly higher readings. I decided to get another probe to make sure. The second probe came up with the same readings so i decided to just run both. At that time I assumed that possibly the heavy air injection via the airstone skimmer (about 4 cfm) and the high position of the drain line to sump, was just helping the level to stay that high, also a relitivly low bioload to water relationship

Whatcha think??


Mike

 

[Boomer]

I sure looks like you are doing everything right

At that time I assumed that possibly the heavy air injection via the airstone skimmer (about 4 cfm) and the high position of the drain line to sump, was just helping the level to stay that high, also a relitivly low bioload to water relationship

It may be this. Have you taken a sample of water from the middle of the tank to see what it reads ? Obviously putting the probe in a sump or somewhere where one is dosing is not a good idea. Mine, sitting the the closet, a MTC sump has a built in probe into a holder. The water from the overflow box spills into a flat try through a preferated tube, the water must rise over that tray and into a overflow tube to the sump. That water als fills to a special probe holder box, The box is always full to the right level with slow flow current and zero air bubbles or air pockets can form because of its design

8 moths is fine for a probe, up to a years or may be if you have treated it well you can stretch it to a year. I hope you like many are NOT using a toothbrush to clean the probe. This a NO-NO. When I told Mike Ross that one of his clients, West Coast ?? was giving out instruction on cleaning probes with a toothbrush he flipped out and called the guy immediately. There is a seal between the probe and the band where the tooth brush can damage it and then there is the ability of the toothbrush to scratch the Platinum, all which can give bad readings. You are better off to clean it with tissue or Q-Tip. Mike's method, was 600 grit sandpaper, stroking it up and down the length of the probe so the probe / band were smoothened out the same

http://www.sensorex.com/support/instructions/download/glassORPElectrodeInstruct.pdf

I guess I just can't see how one could get 425mV or there abouts without ozone

 

[mojoreef]

The main probe sits in the main tank as I have described. I did take a reading from the middle of the tank about the same distance in depth and it came back about the same, higher by 3 points. Sump is about 5 points higher. I have a frag tan that has become an equipment junk yard, in their I have the second orp probe (thats where the skimmer output is) and it stays with in a couple of points to the probe in the main.

For cleaning I just use a piece of tissue paper and a kind of tooth pick.

One thought here might be this. I do run ozone continuously, now I have turned it off for a week at a time. DO you think a week would be enough time to significantly reduce the orp level??


Mike

 

[sharks]

Mike how long is it on before you shut it down for a week?
Just wondering since I just started running it 24/7.
And that may matter for Boomer to answer I think?
S

 

[Boomer]

See you are confusing me I thought you ran ozone allot but with this post I got the idea you have shut it down for long periods and not just a week and it still around 425. Hence my comment you can not get 425 without ozone Lets pretend you have not used ozone for 1 year thing it will still be 425 ?

A week, with your tank and the way you run it no it may not change much and I can buy the 425. Shut it down for a month and see what happens. The other guys I mentioned never use ozone and give values like 425-450. It is some of these guys where I say clean the probe and see what you get.
I do find it verrrrrry odd that you only get a change of, 3, 5, or drops of 2O mV from time to time, unless your pH is very stable 24-7 > Here is a plotted graph fro 24 hrs an look at the flux. But you did say your readings are pH comp for, so that would give a flatter graph. This graph is not comp for pH but if it was it would be more than 2 or 3 mV. But then there is the realllllly big issue ORP is not really understood. It was very hard for Randy to do that article. One should never compare OPR values from tank to tank, is what I always tell people. And if the OPR jumped up or down 10, 20 30, points at some time do not get all excited. Some animal my of just doo-dooded more that day or maybe a male duster spawned out and you missed it.

 

[mojoreef]

And that may matter for Boomer to answer I think?

Yea sharks thats why I said that in my last post, I think that matters to.

See you are confusing me I thought you ran ozone allot but with this post I got the idea you have shut it down for long periods and not just a week and it still around 425. Hence my comment you can not get 425 without ozone Lets pretend you have not used ozone for 1 year thing it will still be 425 ??

I do I run it 24/7/365. Thier are or have been times where it get shut down for a couple of days or even a week or so. During those events the orp still never goes below 425. Thier was also a period where I had it off for a little over a month and could not get it to go below either.

I do find it verrrrrry odd that you only get a change of, 3, 5, or drops of 2O mV from time to time, unless your pH is very stable 24-7

My ph has a range of between 4.5 and 8.3, low of coarse being dark . My unit is ph compensated and what I said was that I do get fluxes of 10 to 20 points from light to dark conditions and I get 3 to 5 MV difference between locations of probes.

One should never compare OPR values from tank to tank, is what I always tell people

Compare no, but thier is a huge difference in orp from tank to tank based on its biological filtration methods. In my tank I think I have created more of an enviroment conducive to oxidizers. As in Ozone, high air injection, high aeration via drain lines and so on and then overall high flow. The opposite of my tank would be a low flow, low skimming DSB style tank, this tank would be more conducive to reducers.??


MIke

 

[Boomer]

My ph has a range of between 4.5 and 8.3, low of coarse being dark [

At a pH of 4.5 how do you control the nomal melting away fo corals

 

[mojoreef]

ROFL ooops. that was supposed to be 8.45


MIke