ORP Level

[hskim]

ORP

I have question about ORP in Reef Tanks. Form what I hear adding O3 to water raises the ORP and make the water clearer but from my experiment ORP is low in new clean salt mixed RO/DI water and it is high in old dirty tank water.

I do not use Ozone but I wanted to know the ORP level in my tank water and bought Hanna¡¯s pHep5 Ph/ORP meter. The ORP level used to be 270 or so in old tank water but every time I do water changes it drops to about 143. I do one water change per week with about 7 gallons of fresh salt water made with Instant Ocean Salt. But every time I miss a water change and leave it for two weeks the ORP goes up real high and soon as I do a water change it goes way down.

Am I missing some info here? I read several articles on adding Ozone but something like this was not mentioned anywhere.

I just wanted to know that my experiment was correct.

Thanks

 

[Billybeau1]

The ORP of freshly mixed salt water is around 220 mv or so. So it stands to reason that everytime you do a water change your ORP drops for awhile.

 

[Randy Holmes-Farley]

ORP and clarity of water are not directly related, as the low ORP in some new salt mixes demonstrates.

ORP has to do primarily with the state of metal ions in the water, while clarity usually reflects light absorbing organics.

It just coincidentally happens that ozone and a few other things that increase water clarity also raise ORP.

I do not believe that ORP per se is an important thing for aquarists to target a specific value for.

I discuss these issues here:


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

Ozone and the Reef Aquarium, Part 1: Chemistry and Biochemistry
http://reefkeeping.com/issues/2006-03/rhf/index.php

Ozone and the Reef Aquarium, Part 2: Equipment and Safety
http://reefkeeping.com/issues/2006-04/rhf/index.php

Ozone and the Reef Aquarium, Part 3: Changes in a Reef Aquarium upon Initiating Ozone
http://reefkeeping.com/issues/2006-05/rhf/index.php

 

[Boomer]

I see you are here and on my chem forum on FF, so you have all the answers you need.

I will add here, that the Hanna meter needs to be in the garbage can. I have yet seen one that measures OPR right.

 

[hskim]

<a href=showthread.php?s=&postid=8281822#post8281822 target=_blank>Originally posted</a> by Boomer
I see you are here and on my chem forum on FF, so you have all the answers you need.

I will add here, that the Hanna meter needs to be in the garbage can. I have yet seen one that measures OPR right.

May be you did not calibrate it right. My Hanna measures consistantly all the time. My New Salt water and my tank water measure same off by about +- 20 or so. My new salt water ORP is almost exactly the same all the time. May be it is consistant with wrong value.

 

[Boomer]

I have been playing with these meters for almost 20 years and I'm well aware of how to "calibrate" ORP meters. And you can not actually calibrate an ORP meter. When you compare then to a $400 meter they are off quite a bit. As Billy pointed out new seawater mix is around 220 and even 270 mv and you are way off at 143. I have even had talks with Hanna about this meters use in seawater and in their own words it does not far well.

 

[Randy Holmes-Farley]

May be it is consistant with wrong value

Maybe. You can check the calibration with a commercial fluid. Pinpoint sells some, as do others.

 

[Billybeau1]

Red Sea sells a 450 mv fluid. Marine Depot sells it. Very inexpensive to insure accuracy IMO.