Oxydative Redox Potential (ORP)

Before reading this description it may be useful to read ‘Aquarium pH.’ This can be accessed by clicking on Articles (top of page), then scrolling down to the section named Water Quality.

Initially it should be stated that the aquarist has no need to delve into ORP unless there is a wish to, or the aquarist has advanced enough to believe that understanding will be of value.

The Redox Potential (RP) can be measured by means of a probe, and is measured in millivolts (mV). (The pH can also be measured likewise in mV.) The RP and pH of an aquarium are interdependent.

At RP 300 (pH 8.2) the seawater is considered to be moderately polluted. The RP relates to the pollution load and pH. At a pH of 8.2, if the seawater is polluted, the RP could measure less than +100mV.
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  1. I have to respectfully disagree with many of these conclusions.
    The Redox Potential (oxidation potential) describes the ability for the loss of an electron by a molecule, atom or ion to the gain of an electron by another molecule, atom or ion. Without this ability to gain electrons many minerals cannot be absorbed and properly assimilated.

    A positive Redox or Oxidation describes the loss of an electron by a molecule, atom or ion

    A negative Redox describes Reduction which is the gain of an electron by a molecule, atom or ion

    Oxidized water with its Redox potential of +700 to +800 mV is an oxidizing agent that can withdraw electrons from bacteria and kill them.

    HOWEVER, reduced water with a Redox Potential of -250 to -350 mV readily donates its electrons to unusual oxygen radicals and blocks the interaction of the active oxygen with normal molecules. Substances which have the ability to counteract active oxygen by supplying electrons are called scavengers. Reduced water, therefore, can be called scavenging water. Reduced water inhibits excessive fermentation by reducing indirectly metabolites.

    The bottom line is long term high Redox is not beneficial to life in the aquarium and should be avoided.

    Please see this article: http://www.americanaquariumproducts.com/Redox_Potential.html

  2. Hi.
    Thanks for the input and the link.
    A difficulty faced on a site such as this is to attempt to keep everything at its basic level. A very knowledgeable person would consider ‘basic’ to be too simplified. A point was made on the basic nature. I know there isn’t any comment on this but I thought I would explain why it is done this way. A sort of ‘research further if you wish to’ approach.
    The – redox potential level for a denitrator was taken from the reference given.
    A too high redox potential is not desirable. The highest level given as an example is +300.
    A caution is given about ozone, and also about raising the level being potentially harmful within the aquarium.
    The hope is that the basic workings will be understood along with the potential dangers. Further consideration of the problems/advantages can be made if desired.
    It is pleasing that interest is taken such as yours, and thanks again for the link.

  3. Great info. Lucky me I found your website (stumbleupon).

  4. Hello Bo. Glad you’re here and like the website.

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