Redox and ORP

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Anonymous

Guest
Sorry Jim - Cant help you with that one. Never dealt with ORP in my tank. I believe ozone will help to keep it stable...not necessarily increase it, but not sure. Believe a low ORP indicates a high organic load, not necessarily low water quality.

Low pH also goes hand in hand with low ORP.

The only detailed stuff I remember seeing, was some of Thiels: (somewhat dated, shrug...). Also found something on #reefs once....
http://www.athiel.com/lib5/redox.htm http://www.athiel.com/tips3.htm
http://www.reefs.org/library/talklog/e_edelman_080397.html
http://www.automatedaquariums.com/tecorp.htm

general junk: http://www.analyzer.com/cd/theory/oxygenreductionprinciple/oxygenreductionprinciple%20.htm http://www.ionode.com.au/Techorp.html http://www.chem.uidaho.edu/~honors/redox.html

hth a little,

-Steve
 
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Anonymous

Guest
Is there a setting to turn on a pH and ORP compensation in the setup menu for ORP? I once had a reading of about 280 mV and then realized that the ORP value wasn't compensated for the pH reading. It jumped up to about 350 mV after turning on this setting. If it's really that low, you might want to just get more aggressive about carbon, skimming, and water changes. My tank value floats around 350-380 mV.

Some people advocate the use of dilute hydrogen peroxide to help breakdown some organics and increase ORP, but I won't try it because it's such a strong oxidizer.
 
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Anonymous

Guest
Thanks, Steve.

Like usual, the articles contradict each other. Thiel claims that hydrogen peroxide drastically lowers ORP, Edelman claims it raises it. Hmmm. Thiel says that using it isn't recommended, Edelman says it can be used as an occasional corrective action, but not as regular maintenance. Hmmm again. Bob Fenner says that ORP is also affected by alkalinity but he doesn't say how (up or down?)

Also of interest, Edelman makes the point that false readings are easy to get.

In my case, I added a 30 gal refugium with 6" of new sand the day before plugging in the Neptune. It could be that the new sand bad is sucking up oxygen big time, even though I pumping a lot of air into the refugium right now. I also did a pretty good size water change, which Edelman claims (temporarily) lowers ORP, but it also removes some DOCs which should help raise ORP. It seems most people blame DOCs for low ORP. Lastly, I finally turned on my calcium reactor which is putting some CO2 into the tank and lowering Ph, but that raises ORP according to Edelman. Too many changes at once, but you have to work on the reef when you can, that's life.

Not sure what to do, except maybe wait a few days to see what changes. Frisco, the Neptune doesn't have that capability you mention, to compensate ORP values for Ph (not that I've found, anyway). Do you know what the proper calculation is? Nils and Fossa have a graph in their Vol. 1 that approximates it, but they don't explain how to use it.

Maybe I'll try some fresh carbon and another airstone in the sump, get some O2 into the tank. If anything really interesting develops, I'll post it.

-Jim

[This message has been edited by chapman_jim (edited 29 January 2000).]
 
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Anonymous

Guest
I also think you must be getting a misleading reading for some reason. Unless you have obvious evidence of a reducing environment, like copious growths of cyanobacteria, I suggest leaving well enough alone. even if the reading you are getting is true. Also, I would stay away from ozone generators. I have seen ozone explosions, and even got to put a fire out once, from faulty ozone generators in an atmospheric chemistry lab. Also, breathing the stuff is terrible for your lungs. If you have to increase the oxidation potential, very tiny amounts of potassium permanganate will work. But from what you describe, I wouldn't mess with success.
 
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Anonymous

Guest
I did a search but couldn't find any threads on this topic.

I just installed a neptune controller which measures Ph, Temp, and ORP (Oxidation Reduction Potential). I've never worried about ORP, my animals seem fine and measured parameters are in line. The probe is in the sump near the overflow drain.

Holy cow! It reads 157 millivolts. I look in all the usual books and see that "normal" is between 350 and 400, although all the authors take pains to say that one shouldn't overinterpret ORP values.

My questions are: 1) what have other people experienced with this? 2) what, besides ozone, is used to raise ORP? 3) what's the likelyhood that the readings I'm getting are incorrect, and finally 4) should I worry about this or not?

Any experienced help is greatly appreciated.

-Jim

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No really, hon, this is the last thing I need for the tank!
 
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Anonymous

Guest
OK, I mixed a fresh batch of change water, slightly elevated SG, heated, and aerated for two days. I plopped the probe into this and it measures 162.

Can anyone think of a reason I shouldn't assume I have a bad probe?

-Jim



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No really, hon, this is the last thing I need for the tank!
 
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Anonymous

Guest
From what I understand it takes several days for a probe to stabilize and give an accurate reading.
 
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Anonymous

Guest
I would not worry about ORP unless you have pH and alkalinity at optimal levels. They are much more critical factors as far as the corals are concerned.
Mike
 
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Anonymous

Guest
It may take a week for the new probe to stabilize in my experiance. Did you calibrate it first as new probes need to be calibrated. When we first hooked up our Octopus 3000 up we saw the same thing and about crapped. We did not do anything and a week later it was 375.
If your reading turns out to be true then fix it insted of trying to overcome it with ozone. Ozone generators are as close to snake oil as you can come IMHO and they wreak havoc with plastic in your system.
 
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Anonymous

Guest
I thought of one other thing: If you use sodium thiosulphate to get rid of chlorine, this will pretty radically lower your oxidation potential (or raise the reduction potential).
 
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Anonymous

Guest
The addition of any oxidant, whether it be oxygen, ozone, peroxide, permangenate etc will increase the ORP reading. Problem with using any of these, with the exception of the first, is they are oxidants. And oxidant don't care what they oxidize, whether it is some protein dissolved in the water, or the cell membrane of one of your system's inhabitants Ozone is probably the best one to use, because you can ensure that none makes it actually into the display tank with all your corals and fish.

Hope this is of some assistance.
 
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Anonymous

Guest
Aquaman, as to calibration, the instructions on the Neptune state that the probe is "factory calibrated" and doesn't need calibration, so there is no feature to allow you to calibrate it or even put in some constant offset as with the temperature probe. Ph of course is a different issue.

The probe is manufactured by Pinpoint if that makes any difference.

The probe has been in use now for three days. I don't see it stabilizing at all, it stays pretty much around the same values, just fluctuates about 10mV between night and morning.

DBW, as another test, I took some of my fresh mixed seawater, that read about 162mV, and dumped in three drops of 3% Hydrogen Peroxide (this is in about glass of water). According to the article by Edelman, who says to use 1-2 drops per gallon, that should have blown the ORP off the top of the scale, but it raised the value only to 200mV, so I'm really thinking I have a bad probe.

I'll give it until the middle of the week, and then send it back to the dealer.

Flounder, I don't use a chlorine neutralizer, I use an RO unit for my water, so that isn't it, but thanks anyway.

Anybody else out there use the Neptune Systems Aqua Controller?

-Jim
 
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Anonymous

Guest
Jim,
I use the Aquacontroller you are talking about. I also agree with Aquaman. It does take a few days for the probe to stabilize. First and most important thing is: How does your tank look? If it's fine do not stress. Do not strive to get perfect redox levels. Been there done that! I have used ozone also (at very small amounts) and noticed nitrate levels came up from what was 0 before. Also noticed that if I had just waited the low redox level out (kept a close eye on inhabitants)it would fix itself.
Over the past 3 yrs I've been running the controller my levels swing between 320 & 385.

Definateley call Kurt @ Neptune and talk to him about your problem. Neptune's customer service is excellent to say the least. I have spoke to them in the past about this subject & other things. HTH

Paul
 
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