What does ORP stand for and how important is it to monitor?

ORP stands for Oxidation Reduction Potential. Measured in millivolts (mV), ORP is the measure of your aquarium water's ability to breakdown waste products.

Hobbyists running an ozonizer with their aquarium system will keep a close eye on ORP. Others may never check it. It's a bit complicated so for brevity's sake, we'll give you a synopsis and if you want more info you can follow up with your tank specifics and we can better answer your question.

The best method to monitor ozone input is by measuring the ORP with probes or by a Redox meter/controller. The term Redox potential refers to the electrons transfer from one substance to another that takes place in every chemical reaction. The substance that receives electrons is said to have been oxidized, while the one that loses electrons is said to have been reduced.

In sea water, many of these so called ‘redox reactions’ occur simultaneously. Because of the constant exchange of electrons the amount of prevailing oxidative or reductive reaction can be measured as a voltage, by means of a platinum electrode and a volt meter. The higher the redox potential, the greater the oxidizing capacity of the water.

In sea water the redox potential is between 350-400 mV. Redox potential values of between 300 and 350 mV are recommended as the desirable level, which indicate an oxygen rich environment with low dissolved organics. The redox potential can therefore be used as an indication of the quality of your aquarium environment. Values below 200 mV indicate an accumulation of dissolved organics and a low oxygen level.

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