Redox In Aquariums

From the full article:
THE REDOX POTENTIAL IN AQUARIUMS (& PONDS); How Redox Balance Relates to Good Aquatic Health

(With Permission from Carl Strohmeyer)

Revised 12/7/19

Aquatic Redox Overview

Redox Basics, reduction, oxidation Unfortunately this aquarium/pond parameter is Not a well known process among many aquarists, the implications of Redox for a healthy aquarium are quite far reaching, and thus important for any aquarist considering moving from basic aquarium (or pond) keeping to advanced to understand.
Aquarium keeping professionals used to believe that a higher oxidizing Redox was best, but much research as well as observations and tests have shown this to simply not be true, rather a balanced Redox.
Unfortunately many aquarium keepers still subscribe to this view, especially those who only get their information from aquarium keeping forums, even though there is so much evidence to the contrary, especially in human medical research which has shown higher Redox in sick patients than in healthy patients (especially with cancer).

Redox, also known as Redox Potential, oxidation potential, & ORP (oxidation reduction 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. So it is very important to keep a healthy Redox Balance via proper dissolved oxygen levels, UV Sterilization, and proper positively charged mineral levels (such as Calcium and Magnesium).
(Please click on the picture above/right to enlarge for a better view)

These three factors have the most affect in Redox Balance Maintenance in Aquariums and ALL are important

  • Water Changes; this is the most obvious and simple, however this is often not sufficient and sometimes the new water used does not have adequate mineral ions (especially if RO water is used even in part), so supplementing with mineral replenishers (such as SeaChem Replenish, AAP Wonder Shells, Instant Amazon, etc.) even during water changes may be necessary.

    Product Sources:
    *SeaChem Replenish Trace Mineral Ion Supplement
    *AAP Wonder Shell; Aquarium Mineral Ion Replacement Block

    IMPORTANT! There are many sellers such as via Amazon and other discounters that have attempted to get on the Wonder Shell bandwagon sell clearance Wonder Shells [as a the genuine product is one of the best methods to provide mineral Cations to balance Redox], it is worthy of note that Wonder Shells lose their Cation charge slowly, so purchasing clearance product to save a few pennies or because you are too lazy to purchase outside of Amazon, you are likely then just throwing your money away.
    The ONLY full line (including Medicated) of authorized AAP Wonder Shells is American Aquarium Products. These are fresh product that are rotated in inventory with new stock every month.

  • Addition of positive mineral ions in between water changes, especially during times of stress or high bio loads can increase the Redox Reduction to counter oxidative affects on fish.
  • UV Removal of oxidizers in aquariumUse of a true UV Sterilizer which impacts Redox Balance in a different way than water changes or additional minerals; the UVC irradiation destroys destructive oxidizers in the water column which can otherwise add oxidative stress to fish. This is done by changing the magnetism of the water, also sometimes referred to as magnetically charged water.
    This can be seen in the picture to the right

    It is worthy of note that with the influx of cheap UV clarifiers masquerading as true high dwell time level one UV Sterilizers sold via Amazon, eBay, AquaTop, etc; that these will not help with this aspect of Redox maintenance.

    This unfortunately is an area again where some reef keeping forums that are still in the dark ages have not caught up to human studies in Redox and rH.
    A High Dwell Time UV Sterilizer works similar to the ozone layer in our upper atmosphere (except in reverse); although the UVC emitted by the sterilizer is itself an oxidizer, the interaction of the UVC inside the unit with oxidizers such as ozone is such that the UV Sterilizer REDUCES these oxidizers and free radicals as well as potentially magnetically charges the water.
    This was confirmed by Dr. Mamoon Kundi in an email he sent to the author of another Redox article I quote from often in this article as per his work using UVC to balance Redox in human studies, and thus improving immune function.

    Reference: Aquarium Redox; Background


*Oxidation describes the loss of an electron by a molecule, atom or ion
Example: Redox processes such as the oxidation of carbon to yield carbon dioxide.

*Reduction describes the gain of an electron by a molecule, atom or ion.
Example: The reduction of carbon by hydrogen to yield methane (CH4).

Another example: Calcium or Magnesium which initially are composed of positively charged atoms immersed in a sea of movable electrons may have given up all possible electrons to cells under oxidation. It is for this reason, then, that calcium and magnesium supplies must be constantly renewed; without this “fresh” calcium (positively charges calcium and other mineral ions), etc. your Redox balance will suffer.

Think of it this way; a storage battery “works” only when a positive and a negative electrode are present to maintain an electrical current. When the positive plates become exhausted, the battery is no longer any good (even though the metal plates and other “ingredients” for the battery are still present; so it is that your GH or Calcium Test may show adequate minerals, but these minerals have been oxidized an thus rendering the test inaccurate).

The above are over simplifications of the process, so please read on as I will go into further depth as the article progresses, especially as Redox relates to aquatic health.

Oxidized Water:
Oxidized water with its Redox potential of +700 to +800 mV is an oxidizing agent that can withdraw electrons from bacteria and kill them. The oxidized water can be used to clean hands, sterilize utensils, and treat minor wounds.

Here are a few oxidizers: ozone (O3; Oxidation potential= +2.1), hydrogen peroxide (H2O2; Oxidation potential= +1.82), chlorine (Cl2) and chloramines (NH2Cl).
Further Reference: Aquarium Medications, Part 3, Chemical Treatments, Hydrogen Peroxide

Reduced Water:
Reduced Ionized 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.

Here are a few reducers, in other words, elements or processes that transfer electrons to another substance;
Magnesium, Calcium, Sodium, and the process of Photosynthesis which involves both oxidation and reducing.

Elements such as most metals, as well as essential elements for aquatic life; Calcium and Magnesium are major reducers however because of this they are also most easily depleted. It is noteworthy that elements with the highest reducing or oxidation potential are also the most easily depleted in their oxidation or reducing properties.
Reference: Aquarium Chemistry, Calcium, GH, KH, pH, Positive Mineral Ions

What is important to note, is that although oxidation is a necessary part of biochemistry for fish and all animals (such as for energy production), the normal healthy state is one of reduction. During normal biochemical processes molecules that are normally reducers give up their electrons (in much the same way a car battery does until re-charged), so without a recharging via the addition of new minerals that are high in these electrons or even processes such as UVC sterilization (or even high PAR lighting), your aquatic biochemistry will suffer and eventually so will your fish!
Further Resource: Aquarium Lighting; PAR

It is noteworthy that even if you have a UV Sterilizer, but fail to change your UV Bulb every six months, this tool for a balanced Redox will quickly become less effective.

Product Sources:
*Level 1, Redox Balance Capable UV Sterilizers
*UV-C Replacement Bulbs; High Output, Level 1 Capable

One more basic generalization to consider before reading the more in depth article is this: Water that is of low pH (acid), in general, measures high ORP while water of high pH (alkaline) measures low ORP. However, in natural water (generally spring water), acidity of minus ions and alkalinity of plus ions can coexist.
More about this subject here:
Natural Redox.

It is important to note that Aquarium Redox can be a complex subject with some basic principles to also understand, however this is a subject that simply reading one section of this article will yield incomplete information. For this reason I recommend reading the whole article.

For the full article (including management & summary) please follow click here:

I also urge my readers to read this article about ultraviolet sterilization use in an aquarium or pond. This is an IMPORTANT read if you are even remotely considering the purchase of a UV Sterilizer, especially since the market of late has been flooded by mostly cheap ineffective UV Sterilizers!

Aquarium or Pond UV Sterilization
“UV Sterilization”

AAP,Hanna ORP, PH, Temperature Meter H198121
For readers seeking to step up to a higher level of Redox awareness in your aquarium, including the even newer studies in rH (relative Hydrogen) and its importance in measuring Reddox in aquariums, I might suggest a good Redox Meter such as the one pictured to the right.

Product Resource: AAP/Hanna ORP, PH, Temperature Meter #H198121

Further Reference:
Magnetically Charged Water


* How Aquarium or Pond Fish Medications Work
A top notch article that starts off with this page (1) about use, types, what to do and not to do and then breaks into 3 more separate web pages with even more specifics

* Aquarium Lighting; Complete
This is easily the most complete and authoritative article on the subject of aquarium lighting. It is noteworthy that there is evidence that correct lighting has a positive effect on aquarium Redox Balance

* Aquarium Nitrogen Cycle
One of the best articles on the subject of the nitrogen cycle for fresh or saltwater aquariums

*Aquarium Sponge Filters
These Patented AAP/ATI Sponge Filters are FAR SUPERIOR to the cheap Chinese knock offs unfortunately sold now in many locations.

*Pond Algae

*Pond Care, Information

Copyright 2019, By Steven Allen

7 responses to “REDOX IN AQUARIUMS

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  7. Hi,

    Could you please take a look at this and hopefully edit your article? There is no such thing as magnetically charged water.


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