ORP or redox potential

ORP (redox potential) in the marine aquarium

Introduction

The oxidation-reduction potential (ORP) of marine aquariums is a measure of the oxidising power of the water. It is often recommended to hobbyists as an important water parameter, and some companies sell products (equipment and chemicals) meant to control ORP. Many of those who recommend controlling ORP are hobbyists convinced that it measures the relative "purity" of the aquarium water, even though this is far from certain...

1. 1The tank water tends to gain or give up electrons
2. 2Platinum electrode in contact with the water
3. 3Reference electrode the point of comparison
4. 4Meter reads the difference in millivolts

ORP is an electrical potential, measured in millivolts against a reference electrode.

Sources: [1]

1. 1Many substances together give a mixed potential
2. 2Temperature and pH change the reading: note them down
3. 3A single number shows intensity, not capacity
4. 4Purity? for the author it is far from certain

A single ORP value does not describe the whole water: in natural waters it is only a semi-quantitative measure.

Sources: [1]

Keep reading the article by clicking the button below (the document is in Italian):

Sources

1. U.S. EPA Region 4, Laboratory Services and Applied Science Division (2024). Field Measurement of Oxidation-Reduction Potential (FSBPROC-113-R5). U.S. Environmental Protection Agency.
2. Li X., Blancheton J.-P., Liu Y., Triplet S., Michaud L. (2014). Effect of oxidation-reduction potential on performance of European sea bass (Dicentrarchus labrax) in recirculating aquaculture systems. Aquaculture International 22(4): 1263-1282.
3. Li X., Przybyla C., Triplet S., Liu Y., Blancheton J.-P. (2015). Long-term effects of moderate elevation of oxidation-reduction potential on European seabass (Dicentrarchus labrax) in recirculating aquaculture systems. Aquacultural Engineering 64: 15-19.