What is ORP?

[clown]

I m looking to buy an aquarium controller. I see a lot with ORP probes. What is ORP? Do you use ORP, and what are the PRO's and CONS?

 

[Pneumatic]

"Oxidation Reduction Potential"

I wondered the same thing a while back and started looking into it. I found this but I nodded off mid article so I am really not clear on the concept. See if you can make it all the way through.

http://reefkeeping.com/issues/2003-12/rhf/feature/index.php

Any time you start throwing things like this at me:

2Fe+++ + Cu ßà 2Fe++ + Cu++

My eyes glaze over and I just nod in agreement like I know what you are talking about. That's my little secret so don't tell anyone.

 

[DaveJ]

@clown wrote:

Don't worry about it. In my opinion its a useless reading and while it is nice to see what it is, to make sure its not dropping into the basement, doing anything to the tank to maintain a certain number or range is not needed. If the package comes with the ORP probe, mine did, fine. But don't go out the way to get one.

 

[Serk]

Two times it's really nice to monitor ORP:

#1. If you dose ozone, IMHO, you should only do this via an ORP controller.

#2. When you feed the tank, the ORP temporarily plummets. This can be VERY handy. When I was in Africa for a month, my lovely wife had promised to feed the tank every 2-3 days at least. I was remotely monitoring the ORP level, and noticed I didn't see any dips like I would if the tank had been fed, in almost 2 weeks... I called her on it. (HOW did you know when I last fed the tank?!?!?! Where's the webcam? WHERE is it!!!)

 

[Wes]

ditto on number one. this is the reason i got the ORP probe with my controller is because i want ozonne on my big tank eventually. ozone can make tank water look clearer. read up on it thoroughly before you think about dosinng it.

and kudos on number 2, learn something everyday. thats an interesting tidbit.

 

[psteeleb]

ORP (oxidizer reduction potential) is a measurement of the constant battle that goes on between oxidizers and compounds the oxidizers break down (mostly organic)

there are a lot of oxidizers in our systems the most prevalent is oxygen, but ORP does not a numerical measurement of these oxidizers, it measures a balance. In other words more organics and more oxidizers can give the same reading if both were lower. For example; if you suddenly had no organic compounds in your system ORP would skyrocket without any increase in the number of oxidizers. On the flip side add organic compounds (something dies or feeding time) and ORP drops.

You can increase ORP by increasing the oxidizers like ozone, chlorine, etc but as you increase oxidizes you sterilize the system to a point where noting can survive as the oxidizers will start to break down living tissues.

As mentioned ozone provides the benefit of breaking up heavy organics improving water clarity and skimmer performance but it has to be controlled. Measuring ORP is the preferred method. ORP in a normal well oxygenated system will usually run around 300, with ozone, people that use it will usually run it up around 350ish.

Without Ozone ORP provides another system health indicator. It can show you that something can be wrong in the tank; like a sudden drop of ORP could be due to a lack of oxygen due to consumption (see one of Marc's posts lately due to vodka and vit C dosing), or a sudden increase in organics due to something dying.