Redox potential - how it relates to aquatic health.

Discussion in 'Reef Chemistry Forum' started by jlaw, May 17, 2012.

  1. jlaw

    jlaw New Member

    May 10, 2012
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    North Carolina
    I came across this article, it's a great read.

    Although not a well known process among many aquarists (with still much misunderstanding of both sides of the equation by even advanced aquarium keepers); 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.
    As well even the average aquarist should consider this water parameter when all other parameters check out, yet fish continue to be susceptible to disease this may be an important parameter to consider (as growing research in human disease resistance, and even plant growth also shows, yet the aquarium keeping community still seems to be in the dark ages as per this research)

    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)

    As another note to think about as you read this article is Redox Balance, as many in the past have stated exact numbers such as +300 mV being the so-called "best" Redox reading for a marine aquarium. This is incorrect in so much this may be a good Redox Reading to obtain (for oxidation) when high organics and decomposition is lowering water quality, HOWEVER for a new or established aquarium that is properly functioning this is not a number you should be "shooting" for correct Redox balance, so please read on!.

    *Oxidation describes the loss of an electron by a molecule, atom or ion.
    Another way to look at this is to lose or cause to lose hydrogen atoms.
    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.
    Another way to look at this is remove oxygen atoms or add hydrogen atoms.
    Example: The reduction of carbon by hydrogen to yield methane (CH4).

    Another example: Calcium (Ca2+) or Magnesium (Mg2+) which initially are composed of two positively charged ions 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, 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 as per positively charged calcium ions).

    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).

    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. Please note that the oxidizers have a plus and the reducers have a negative in the chart to the left. Click graph to enlarge

    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 involve both oxidation and reducing.

    As one can see from the graph that 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 (the elements at the top and the bottom of the graph are most easily depleted in their oxidation or reducing properties).

    Simple Test to Understand Redox: Take an 8 oz. glass of water, then add enough Potassium Permanganate (Jungle Clear Water) to change the color to a mild red, then take any aquarium water conditioner (such as Prime or Start Right) and slowly add drops to the water and watch the red be "reduced" (neutralized) to a clear brown color.
    What you are observing is the reduction an oxidizer (potassium Permanganate) by a Reducer (generally Sodium Thiosulfate is used in these conditioners).

    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!
    As per UVC energy, Wolfgang Ludwig (a physicist and advisor to World Research Foundation,) made this quote:
    "Water quality can also be evaluated by the amount of ultraviolet light it absorbs; “poor” quality water will absorb higher amounts of UV light, while “good” quality water absorbs low amounts."

    One more basic generalization to consider before moving on in more depth 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 in Natural Redox). (See this website for more; Understanding pH and ORP)

    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 (as well as links provided) for a more thorough understanding (it may take more than one reading as well)
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    My research and interest in Redox goes back to my curiosity as to why certain aquarium maintenance methods were more effective in keeping healthy fish, and the common knowledge did not fully explain results I was achieving.
    I base this article on studies about the Redox Potential as it corresponds to humans and all fish/animals, even plants. I have found from practical experience and research that a lot more can be learned from medical studies or other university level studies than from many anecdotal aquarium articles and sadly some otherwise excellent forums (these articles/forums usually just take bits from another article without any real research, often with old ideas being simply regurgitated).

    Originally my statement was: “I do not believe this is a subject that many aquarists should stress over, but a lot has been learned about this subject since I first started researching this in the 1980s”. However the more I have studied this subject as well as the newest research shows that all aquarists should have at least a basic understanding of this subject as it has major implications for fish and aquatic health that often go against commonly held anecdotal aquarium keeping beliefs; such as so-called correct GH (which includes essential positive mineral ions), effect of UV-C in the magnetic charge of water, and positive vs. negative Redox.

    I have also had to change my opinions about this subject based on newer evidence. One such opinion was “should you have a positive or reducing Redox”. I based my earlier opinion on a higher Redox of +300 mV based on many studies of ocean waters and simply repeating what I was told, but newer human research and my own tests over the last 15 plus years have lead me to where I am now that a BALANCED Redox is important (as of this writing, both oxidizing AND the less known reducing Redox play important roles in fish health).
    What is a balanced Redox? The best research indicates a Redox reading between +125 to -200 mV (a higher Redox is sometimes needed when oxidation is necessary due to high organic de-composition)
    See the chart below (ecologically safe water):

    What is Mineral Redox Water?

    Maintaining a proper Redox Balance (or Potential) which includes the reducing side of the equation is a lot like having an anti-oxidant vitamin in the aquarium water (although a more accurate description would be properly magnetically charged water). The Aquarium Redox is also just one more parameter towards good disease prevention and long term fish health and growth. Please see this article about Aquarium Disease prevention; “Aquarium Disease Prevention” .

    Looking at the oxidizing side of the Redox equation (oxidation); Bleach and Potassium Permanganate are oxidizers (Potassium Permanganate is often used for disease treatment an water clarification is ponds and aquariums), however you would not want your fish living in a constantly oxidizing environment for long term fish health, rather you would want your fish in a balanced redox environment which includes a Reducing environment where free radicals are not damaging the cells of your fish and causing problems with Osmoregulation.
    An oxidizing environment is what you get with a positive Redox and is OK (& necessary) for short periods such as during disease treatments however you would not want to keep your fish in constant medication any more than in a constant oxidizing environment (PLEASE read the section about Natural Redox including the quote and outside Redox for a better understanding of this concept)!
    Another IMPORTANT consideration is a healthy Redox affects the electrolyte balance in your aquarium. Calcium as well as Magnesium are both important reducers, however they are both easily oxidized as well (please see the chart in the Redox Potential Basics section). So for proper reduction, these elements (with a positive ion charge) need to be replaced on a constant basis (read further in this article for more on this subject).

    What got me started researching this was I have noticed and documented differences with aquariums (I mostly used goldfish for these tests) with regular water changes, UV sterilizers, added minerals/ electrolytes (such as Wonder Shells or similar methods/products), but was not sure why health, vitality and especially disease resistance were improved.
    The goldfish had less incidence of such general diseases as well as such infestations as Ich, Anchor Worms and other problems, which the use of UV sterilizers cannot truly eradicate due to difficulty killing them in the UV itself and that parasites such as Anchor Worms do not get readily caught up in the water column.

    The Redox Potential explains a lot of the results I was getting as the fish have a better ability to resist a disease sometimes simply by having a healthier immune system and osmoregulation.
    This pertains to a Balanced Redox potential (which includes a proper magnetic charge in the water) that I have found a properly installed and constructed UV Sterilizer aids in maintaining as well as proper mineralization of reducers and constant replenishment of these minerals, such as calcium, and regular water changes. that lower nitric acid and DOC levels (dissolved organic compounds).

    In further research I noted that a proper Redox Potential improves the health of humans AND fish. A Redox Potential in the -200-400 mV range in human studies has been shown to have the same affect as anti-oxidant preparations such Vitamin C (and many others). In medical studies the enhanced oxidizing environment can facilitate the binding of pathogens or antigens to effector cells (a type of lymphocyte that are actively engaged in secreting antibodies) leading to a hyper-responsive innate immune system. Previous work has shown that an oxidizing environment leads to enhanced release of super-oxide and nitric oxide, activation and translocation of nuclear transcription factor and enhanced production of cytokines (proteins and peptides that are signaling compounds produced by animal cells to communicate with one another). The creation of a markedly reduced environment by addition of antioxidants blunts all of the above primary responses of the innate immune system.

    This shows that the health of aquarium fish can be maintained by a UV Sterilizer not just by the killing of potential disease pathogens, but by the effect UVC has on the Redox Potential of an aquarium (as well as positive mineral ions/magnetic charge of the water). I have been observing many aquariums of such "ordinary" fish as goldfish, both with and without UV Sterilizers (keep in mind that some UVs are useless by design and installation), and the goldfish with every other factor equal (such as mineralization and water changes) that had a UV Sterilizer installed, were generally much healthier.
    The 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. For those interested in checking this out, simply add potassium Permanganate into a tank with a UV Sterilizer and one without. The tank with the UV Sterilizer clears MUCH quicker!

    Unfortunately the aspect of Redox Balance and Ultra Violet Sterilization is often missed my many aquarists, and sadly many otherwise well informed reef keepers.

    See this outside article for UVC/UVB healing therapies in humans now being proven in tests! Oxygen Healing Therapies with UVC

    Back to my many tests with goldfish tanks over several years in the 1990s; I ran these tests with many different filters and combinations there of.
    Cleanings were a constant of every two weeks with about 25% changes of water via a Gravel Vacuum. Feeding was performed at the same intervals with the same food (at that time Hikari and Spirulina 20), and all the tanks had the same number of goldfish at as close to the same size as possible.
    I found the tanks with the Under Gravel Filters performed the worst (and not just in Redox) due to their tendency for DOC (Dissolved Organic Compound) buildup which results in high amounts of Nitric Acid production. UG Filters performed better when combined with a UV Sterilizer and another filter such as a canister filter, however the tanks that performed the best did not have UG filters, rather a combination of two filters (generally a Sponge Filter or Fluidized Filter were part of this combination) AND a UV Sterilizer.
    Some of the tanks were maintained with added minerals/electrolytes, some were not.
    The best results as per long term health were achieved where minerals cations (positive mineral ions) were added on a constant basis vs. methods that required weekly or similar dosing requirements or non minerals at all.

    Often maintaining a good Balanced Redox (for both saltwater and freshwater) can be as simple as good aquatic husbandry: water changes, proper electrolytes and minor elements in the water, using simple reducers such as Sodium Thiosulfate, Calcium and Magnesium when necessary. Delivering these reducers on a constant basis along with the use of UV Sterilization can improve your Redox.
    That all said, please read the rest of the article before I over sell any one on a UV Sterilizer, Mineral Blocks (such as Wonder Shells), or drip mineral applicators (products such as SeaChem Replenish can be mixed with water and dripped into the aquarium). As often good aquatic husbandry is a major factor in a healthy Redox Potential (balance).

    Another interesting aspect of Redox potential is the correlation of a certain Redox level and the growth of Blue Green Algae (Cyanobacteria) in Aquariums and lakes. This is an on-going study however Redox does SEEM to play some role in the aquarium and lake “plague”. For more information about this, I recommend reading this article:
    Blue Green Algae (Cyanobacteria) in Aquariums; what it is and how to control it. Currently this is just an opinion/theory though.
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    NATURAL REDOX Including Human Studies:
    Over geologic time abiogenic (not biological in origin), biogenic (produced by living organisms) and anthropogenic (processes are those that are derived from human activities, as opposed to effects or processes that occur in the natural environment without human influences) deposits were accumulated in rivers, lakes and seas. Simultaneously there proceeded the self-purification of natural water on the basis of the chemical reactions of oxidation and reduction. Living organisms such as fish are adapted not to "perfectly clean water", such as distillated water, but to ecologically clean water with definite content of organic and inorganic compounds, micro-admixtures, Magnetised ions, and even bacteria or saprophyte (any plant that depends on dead plant or animal tissue for a source of nutrition and metabolic energy, e.g., most fungi). The range of mentioned components of ecologically clean water is the integral result of oxidation and reduction self-purification of water.

    At the initial stages of this cycle toxic hydrophobic organic compounds (molecules that are repelled from a mass of water) are oxidized to the hydrophilic forms (a molecule or portion of a molecule is one that is typically charge-polarized and capable of hydrogen bonding, enabling it to dissolve more readily in water than in oil or other hydrophobic solvents), which are characterized by the better biological compatibility. Energy of oxidation of degrading organic compounds is absorbed during reduction chemical transformations. Excess of ions of the heavy elements transforms into insoluble, inert, nontoxic forms. Concentration of ions of light elements is stabilized. Just in such water live the water organisms, and land animals drink such water.

    Spring waters, which are considered to be the most clean according to the ecological criteria, are filtered through the rocks and subjected to the oxidation and reduction, sorption and catalytic influence. As rule, they are mineralized and include non-volatile organic substances, which are detected by the permanganate oxidability (expressed by oxidability by potassium permanganate and potassium dichromate).
    Put more bluntly; only water that has been naturally filtered by percolation deep into the earth, heated under pressure to super steam at the mantle and re-imprinted by the clays, gravels and minerals that it passes by on its way to the surface at 4C is fully mature and full of useful electromagnetic energy.

    ORP can change so rapidly, however in a stable condition of electrons, Redox potentials above 400 mV are dangerous to life. Good quality water for life is lower than 350mV, and water of lower than 100mV is effective for disease healing purpose when the part of body is particularly oxidized (harmed) by disease.

    In tests using electrochemical purification, water keeps its initial neutral values of pH, but ORP (Oxidation Reduction Potential) of water shifts toward the negative (electrode or reduction) values. The resulting purified water obtains the antioxidant properties with characteristics of pharmacological activity close to the properties of the antioxidant preparations (a -tocopherol, b -carotene, vitamin C etc.). In case of dilution of polyvitamin preparations in electrochemically purified water ORP of mixtures is decreased approximately by 200 - 400 mV in relation to the control solutions with non-treated drinking water.

    The above partially explains how a proper Redox Potential improves the health of the fish or other aquatic organisms as I have observed. Bringing this back to my observations of goldfish aquariums; All aquariums with the same filtration (canister filter with sponge filter), the same feeding schedule and food, even the same basic goldfish (a mix of Ryukins and Orandas); The aquariums with the quality, properly installed UV Sterilizers (again assuming proper dissolved oxygen levels) not only had less incidence of disease, but general health, appetite, vigor, growth, and water clarity were all improved.

    Here is a Quote about pH vs. Redox:
    Traditionally we have judged the properties of water from the standpoint of pH, in other words whether water is acidic or alkaline. According to Dr. Yoshiaki Matsuo PhD., the inventor of the Ionized Water unit, "In my opinion, Redox potential is more important than pH. The importance of pH is over emphasized. For example, the average pH of blood is 7.4 and acidosis or alkalosis are defined according to deviation within the range of 7.4 +- 0.005. But nothing has been discussed about ORP, or oxidation-reduction potential."
    Source: Alkaline Ionized Water by Dr. Hayashi

    A further point from human studies shows this:
    “Dr. Uchiyama working at a general hospital in Japan conducted a complete medical checkup with his 871 clients, with the result of 92 of normal result (judged healthy) and 279 of requiring further consultation or treatment for their health (judged potentially sick). He measured OPR of all of their urine. Interesting result was found that many of healthy clients showed ORP voltage of +50 to +74 and clients judged unhealthy showed +100 to +124. Healthy persons tended to have lower voltage of ORP, less oxidation potential in their body.”


    I have mostly discussed Redox Reduction and its misunderstood importance, however there does need to be a balance between reduction and oxidation for proper chemistry within a fish or most all living animal organisms. The best current research seems to indicate a Redox reading of approximately +125 (freshwater) indicates a balanced Redox with optimum electromagnetism of the water, however Redox Potential is often in “flux” so I personally believe following healthy aquatic husbandry methods (that consider the affect on Redox) is an aquarists best bet in maintaining this balance, this includes a higher Redox (as high as +350) when oxidation is necessary due to high organic decomposition.

    Bio Chemistry as it relates to Redox Balance:
    There are enzymes within a body that are reactive oxygen species (ROS) and others that are reactive nitrogen species (RNS). A disturbance in the oxidation–reduction state of the cell, in which ROS production exceeds antioxidant defenses, is called oxidative stress. By analogy, nitrosative stress is an impairment in nitric oxide (NO) signaling caused by increased amounts of RNS, which may be caused by or associated with a disturbance in the Redox state. As discussed earlier, free radicals are highly reactive molecules with unpaired electrons. Free radical chemistry is the underpinning of 2 broad classes of signaling molecules in biological systems: ROS, which are reactive intermediates of oxygen metabolism, and a closely related group of RNS. The forms of ROS that are relevant in biological systems include the superoxide radical (O2•–), hydrogen peroxide (H2O2), and hydroxyl radical (OH•). RNS of biological importance include NO, low- and high-molecular-weight S-nitrosothiols, and peroxynitrite (ONOO–).

    Superoxide and other ROS are produced in the mitochondria during oxidative phosphorylation as a normal byproduct of aerobic respiration in fish (and other animals). Superoxide is formed by the 1-electron reduction of molecular oxygen, resulting in a free radical. However ROS are not intrinsically destructive; on the contrary, increasing evidence shows that they play necessary roles in normal signal transduction. In low concentrations, they are implicated as second messengers primarily through inhibition of phosphatases, acting downstream of effectors such as platelet-derived growth factor, epidermal growth factor, tumor necrosis factor agonists, and interleukin. In higher concentrations, however, they take on pathophysiological roles. ROS affect the oxidative modification of diverse molecules, including DNA, proteins, lipids, and sugars, potentially leading to toxicity.

    The problem begins when either ROS (oxidation) or RNS (Reduction) get out of balance and unfortunately in closed aquarium or pond systems this is all too common. An aquarium with poor circulation and low oxygen levels can swing towards poor oxidation while more commonly Reduction is halted by the fish’ body inability to reduce these superoxides.
    Reduction is dependant on production of RNS; NOS3 (endothelial NOS) are found in a variety of cell types and are regulated by binding to calcium and calmodulin (calcium-binding protein expressed in all eukaryotic cells). NOS2 (inducible NOS), on the other hand, has very high baseline affinity for calcium and calmodulin; therefore, its activity is effectively independent of calcium concentration.
    The importance of calcium in this reaction is often missed by most aquarists based on the many emails I get and comments I read on many sadly misinformed aquatic forums.

    As well, the reduction side of this equation can also be interrupted by the oxidation of other reducing chemicals such as ascorbate (vitamin C) and reduced thiols, especially glutathione (a tripeptide). These reduced chemicals become temporarily oxidized when they interact (giving up of their free electrons) with oxidizing agents and oxidizing free radicals.

    A more basic aspect of Redox Balance is the water we use can have a direct impact as well.
    The water we use, whether from the tap or Reverse Osmosis/De-ionized this too can affect your Redox Balance, sometimes negatively. Generally speaking tap water if only altered with chlorine or chloramines may have the necessary mineral cations to bring a poor Redox back into balance, the use of RO or DI water while a very practical way to improve and control water parameters (especially with soft water freshwater species or reef aquaria), one should note that the neccessary mineral positive mineral ions (cations) are using gone and the excess oxygen and more acid water is often way too high of an oxidizing environment.
    For this reason it is often important to re-minerals these water sources with products such as SeaChem Replenish or Wonder Shells.
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    Another way to look at the Redox Potential in aquariums is to the relation of waste particles and acid production, as well as dissolved oxygen and most importantly depletion of key important elements. The more waste, the less Redox Potential (ORP) due to more nitric acid production and the depletion of key elements, but this is an over simplification as there is much more to it than this.
    You really need to look at the electrolyte balance in your aquarium. Calcium as well as Magnesium are both important reducers, however they are both easily oxidized as well (see the graph in the Redox Basics section). So for proper balance, which includes reduction, these elements need to be replaced.
    Obviously high organic wastes also requires an input of oxidation (higher Redox), but this should not be ongoing anymore that you should spend all your time in direct sunlight!

    Simply put, these three factors have the most affect in Redox Balance Maintenance
    • 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, Wonder Shells, Instant Amazon, etc. (even during water changes may be necessary).
    Please note that performing inadequate water changes or worse, only topping off water for evaporation does not adequately replenish important redox reducing ions of calcium or magnesium as most any aquarium is going to utilize these ions at a far higher rate than such a method of adding “fresh” water will ever replenish. The end result of such poor maintenance procedures will result in climbing GH readings, yet your aquarium (or pond) ability to maintain a healthy Redox balance will suffer.
    • 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.
    • Use of UV Sterilizer which impacts Redox Balance in a different way than water changes or additional minerals; the UVC irradiation destroys destructive oxidizers and aids in establishing the proper balance of electromagnetism of water column which can otherwise add oxidative stress to fish.

    Important; what is often missed (including by myself in earlier research), is that although you may test and for instance find high calcium levels in an aquarium via a GH over 300, that does not necessarily mean you have any Redox reduction as I should point out that very basic fact of Redox reduction is the donor (such as calcium) transfers electrons to another substance, and is, thus, oxidized itself. This is VERY key, meaning your GH test (or Calcium, Magnesium, etc tests in saltwater) may tell you that you have ample or even too much calcium, HOWEVER these calcium molecules may have already given up their electrons to other molecules such as fish cell molecules so as to achieve state of balance in aquarium Redox.
    This again is where many (again I have to admit that I have been guilty in the past of this too) will claim that their calcium or other minerals or high enough or even too high (as many still get stressed about the high GH brought on by Wonder Shells, totally missing that these mineral blocks are constantly reducing the water via their donation of electrons!).
    This is also where water changes and UV Sterilization also help as these processes constantly balance out Redox. Since water changes (which also aid in oxidation, which is the other side of the equation) can only be done in intervals (unless you have a flow through system), the use of mineral blocks, or other water conditioners as well as UV Sterilization to keep a more steady flow of electrolyte donation is important.

    With the above statements in mind, one must look at two VERY basic organic chemical reactions that occur in an aquarium;
    (1) As stated in the opening section of this article; “oxidation of carbon to yield carbon dioxide”, this describes the process of nitrification or in other words the breakdown of organic wastes by Autotrophic nitrifying bacteria into ammonia and nitrites.
    The higher the bio load, the more of this process is occurring! So it is imperative to replace elements such as negatively charged ions of calcium, magnesium, etc that are oxidized due to this process. This is where many aquarists “miss the boat” as per reasons for water changes, replenishing minerals, or other Redox Reduction processes that will balance this out. This is also why tanks without good ionized mineralization, UV Sterilization, water changes, etc. will often be MUCH less healthy as per disease resistance!

    (2) As to Reduction as also stated in the opening section: “reduction of carbon by hydrogen to yield methane (CH4)”, this describes the de-nitrification of nitrate as it reduces to nitrogen. This process is more common in Marine tanks but can take place in freshwater in certain places where methane production is not an issue such as filters with anaerobic filtration that allow methane to escape (volcanic rock & SeaChem Matrix provide a good place for this process). Also the growth of plants, especially with strong roots in a sandy substrate allows for de-nitrification/Redox reduction.
    This is an area where Veggie Filters in Ponds shine in their ability to maintain excellent bio parameters. This also to a lesser degree shows where some green algae growth is not all that bad.
    All this said as to Reduction, generally de-nitrification processes CANNOT keep up with oxidation processes necessary for breakdown of organic wastes which is why help is needed via water changes, mineralization, UV Sterilization, etc!
    This is where many naysayers of products such as Wonder Shells, or UV Sterilizers totally miss the point as to how much they can improve water quality. This is also how the use of products such as Volcanic Rock or SeaChem Matrix can also indirectly affect Redox.

    Important! Put another way, there is certainly a time and place for a high Redox (oxidation) as lower oxygen levels from many causes such as high organic decomposition is generally not desirable and this will lower your Redox. This is not what I recommend as a means of a reducing Redox environment. However to not have the proper reducers or creating a highly oxidative environment is also not good for long term fish health. The Redox Potential is always going to be in flux and as yet no scientific equilibrium has been established here. Maintaining reducers such as Calcium and Magnesium in your aquarium is just as important as proper levels of dissolved oxygen (which raises Redox). There is evidence both anecdotal and controlled that proper levels of calcium and other anti-oxidants such as Vitamin C (along with other healthy water parameters) will prevent and even cure Hole in the Head disease (HITH). Redox is an important parameter here.

    As stated earlier, Redox can be more important than pH, there are definitely correlations to pH and the Redox effect on pH. But you cannot make the assumption that if you have a pH of 8.0, that you have good reduction. Just like with GH, where your GH is high, you can still have low pH. The bottom line is that there are relations between Redox, GH, pH, and even kH, but these are still individual water parameters.

    Also as noted in he beginning of this article, this is not a parameter to stress over, HOWEVER, Redox reduction should NOT be blown off as many anecdotal/uninformed commentators do in many aquatic forums. The more I have studied and observed in this subject, the more I feel it should not be ignored.

    Effect on Fish:
    Active oxygen molecules, or free radicals, are produced in the water and the fish’ body. They are extremely reactive and can also attach themselves to normal, healthy cells and damage them genetically. These active oxygen radicals steal electrons from normal, healthy biological molecules. This electron theft by active oxygen oxidizes tissue and can cause disease, these are proven facts! This why the constant hammering by some uninformed aquarists against UVs, too high a GH (which is not always a good indicator of electrolyte balance anyway), and even Wonder Shells is ludicrous. Your GH may test higher than desired but in actuality is maintaining a healthy Reducing Redox via Calcium (Facts about Calcium, an essential reducer), Magnesium, etc.

    Effect on plants:
    In a controlled test conducted with terrestrial plants; plants treated with magnetized water (basically Redox Balanced Water) reacted in a test, with a growth in the order of 20% to 40% bigger than the plants treated with regular water.
    While no test has been conducted with planted aquariums, it is not rocket science to draw conclusions from this study and apply this to a planted freshwater aquarium and the effect of Redox Balance on plant growth!
    Reference: Water Information & Conductivity

    Simple Redox Test

    A simple test of Redox can be performed using Methylene Blue and any reducer such as powdered Wonder Shell.
    Simply add enough Methylene Blue 8 oz. of water to turn the water a brilliant blue (usually one drop). Then add about ½ teaspoon powdered Wonder Shell to the 8 oz. of water and stir. The Methylene Blue will dissipate due to the reducer.

    Taking this test a step further into the real world; again add enough Methylene Blue 8 oz. of water to turn the water a brilliant blue (again one drop), this will be the control color. Then take out 8 oz. of aquarium water and add the same amount of Methylene Blue as in the control glass of water.
    If the color dissipates at all (even the slightest) you probably have a balanced Redox with at least some reduction. Expect to see little color change in a healthy aquarium, although absolutely no color change MAY indicate too much oxidation, while any more than a subtle change may indicate too much reduction.
    This test in no way replaces the accuracy of Redox meter, but it is a simple way to make at least an estimate of your aquatic Redox.
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    In biological systems, the Redox Potential must be kept reduced at all times to perpetuate the life process. In other words, the concentration of DHA (an oxidized form of ascorbic acid), must be kept to a minimum. During injuries or stress which expose body tissues to atmospheric oxygen or disease, several reactions are triggered in polyunsaturated fatty acids (PUFAs) present in cellular membranes which produce hormones called prostaglandins that repair damage. Under oxidizing stress (injury or disease) or impaired ability to manufacture NADH (aging or disease), the concentration of DHA can rise as the redox potential slips. This is a potentially life-threatening state for fish or any other animal.
    The initial rate at which the redox potential falls as DHA increase is initially slow, however as DHA increases further, the redox potential falls faster, becoming progressively more antagonistic to the metabolic processes of life. Eventually; if the process is not stopped, the fish (or any animal organism) and slides down into death.

    This is why even prolonged stress (such as constant harassment by tank mates) can lead to illness and even death and why under stressful conditions having ample reducers such as positively charged calcium ions or UVC sterilization is so important!

    Healthy Redox Potential (Balance) maintenance methods:

    [1] Proper water changes with ion balanced clean water (electrolytes) with a GH of at least 100- 200 (GH will supply many important reducers such as Calcium & Magnesium) and with a kH of at least 50-100 ppm (for control of nitric acid production). A proper Reducing/Balanced Redox is another reason for water changes and is also a major reason to not use drinking water intended for human consumption unless it is properly re-mineralized.
    Removal of organic mulm during cleanings is important as this leads to nitric acid production and high DOC (dissolved organic compounds) which are major contributors to a poor Redox Balance. If your water changes are not effective in removing all organic mulm, consider a re-circulating vacuum (such as the Aquarium Cleaning Machine or the more basic Eheim Sludge Remover) that can drain and then continue to remove mulm that is easily emptied from the micron filter.

    Also ponds with “flow through” or spring fed water sources will maintain a good Redox Potential by virtue of the constant addition of fresh, clean and mineralized water, which is why many lakes will become less “healthy” during the late summer months when stream that feed them “dry up”.

    [2] Good aquarium circulation This aids both sides of the Redox equation, although more so the oxidation side.

    [3] A reasonable supply of dissolved oxygen provided by diffusers on power heads, internal filter, air stones, spray bars on the returns of canister filters, etc. Just make sure you are doing a good job of breaking the surface tension of the water, as this is where gasses, including oxygen are exchanged!

    [4] Proper Calcium, Magnesium, sodium, and general electrolyte levels, THIS IS VERY IMPORTANT! As noted earlier, this is an on-going process and although I stress to maintain a GH of over 100- 200 or even higher (less for soft water fish, higher yet for African Cichlids and Marine), this is also an incomplete picture as recent evidence shows that you may have an adequate amount of Calcium as per your test, but this calcium has given up many of the available electrons and is not aiding in your Redox balance which is why using mineral blocks or similar concepts is so important. This also further disproves the point of many old aquarium myths about too high of a GH, as what your test is measuring may not be he whole picture (such as an ammonia test kit measuring ammonia which is 'bad' or ammonium which is 'not nearly as bad' if this comparison makes since).

    Wonder Shells are very useful since they add important mineral cations on a constant basis. As well products such as SeaChem Replenish, Instant Amazon, or Aragamix can be mixed with water and dripped into aquariums to achieve constant positive mineral ions. However I have not found that the use of crushed coral will dissolve at a rate to supply enough of these minerals to have much affect on Redox Balance.

    I have a good article dealing with GH, Calcium, and Magnesium here:
    CALCIUM, KH, AND MAGNESIUM IN AQUARIUMS; The importance of mineral ions

    [5] A UV Sterilizer is one more predictable and proven tools here (when properly installed), but also not a cure all to otherwise poor conditions. UVs work two ways in my research; [1] they morph oxygen (O2) molecules into Ozone (O3), the O3 quickly degrades, the UV then [2] transfers electrons to substances, thus reducing.
    As a side note it is the Ozone layer that blocks many harmful UV rays from reaching the Earth, this is due to the reaction of UVC and Ozone high in our atmosphere, so by using a UV Sterilizer (which has safely contained UVC irradiation), you break down radicals such as Ozone in your aquarium.

    As noted earlier in this article, please reference this article for more about this important subject: “Aquatic UV Sterilization”

    [6] Good Lighting Although not as common a problem for most marine aquarists, especially reef keepers as these aquarists usually have (& know the benefits) of good lighting, in freshwater aquariums this is often a contributing factor to a poor Redox (and to other problems as well).

    In Reef tanks using Metal Halide lighting, SHO, LED may help, albeit to a lesser degree (as this assumes good mineralization and other factors) with freshwater aquariums using lighting with good output of photosynthetic active radiation (PAR). The reasons are admittedly not completely clear as of writing this article update, however from my observations and tests (as well as research I read in March of 2011), I believe correct lighting plays a role similar to UV Sterilization as explained above, especially (in the case of freshwater where poor lighting is often more common) when lighting with poor PAR qualities which are generally found in lights with approximately 6400 Kelvin temperatures. My suspicions are that although PAR has been scientifically established to be important for plants, it may also play and important role for fish as well (both in electromagnetism of the water and similar to how humans derive the benefit of vitamin D production from sunlight).

    [7] Use of water conditioners (for use in chlorine/chloramine removal) during times of stress (especially oxidative stress) such as Prime which are mostly all Reducers. However these products only temporarily reduce Redox and are not a long term solution. It also should be noted that aquarium water conditioners will often cause temporary cloudiness of aquariums do to their strong reducing abilities, however this cloudiness is short lived in healthy aquariums.
    For more about aquarium water conditioners, please read this article: “Aquarium Water Conditioners”.
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    For Redox problems, possible problems :

    * Driftwood; make sure you soak all Mango Wood or Drift wood for several days in a solution of 2 tablespoons pure salt to 2-5 gallons of water to leach our impurities. Even then if you continue to have problems, remove the wood. Over use of peat can also cause similar problems.

    * CO2 generators if not kept at a balance can also cause problems with the Redox Reduction abilities, this is rare, but worth considering. A good link to help here is:
    Measuring CO2 levels in a Planted Tank

    * An abundance of organic mulm in filters or substrate. Check your cleaning procedures.
    I will also note as per my many tests with goldfish aquariums, I found Under Gravel Filters the worst offenders here with high production of DOC (Dissolved organic compounds), and even with UV Sterilizers these tanks were more difficult to maintain a Reducing Redox environment in.

    * A lack of electrolytes (positively charged mineral ions), as mentioned earlier, Wonder Shells or dripping products such as Aragamix, SeaChem Replenish, or similar can help here, BUT they are not a cure all for other problems.

    * A tank with high nitrates (nitrates are a mild oxidant) will also tend to be high in nitric acid (but not always); a properly cycled tank is important! This also usually occurs with high DOC levels (dissolved organic compounds), regular water changes that remove organic mulm are important here.

    *As noted earlier, good lighting and the addition of UV Sterilizers can play an important role for a balanced aquatic Redox Potential as newer studies have proven that UV Sterilization increases immunity by adding electrons and balancing the essential electromagnetism of the water.
    Although less conclusive at this time, high PAR lighting (usually found in lights with an approximate Kelvin of 6500 K), also aids in replenishing reducing electrons due to depleted reducing minerals.
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    This is a relatively unexplored are of fish keeping, and there is still a lot to be learned here and I have to admit having to change my opinions based on newer evidence (I too thought that only a high positive Redox should be maintained), my research is still ongoing and I try and read whatever I can on this subject, especially from outside the aquarium hobby, even if it may not fit with theories I hold.
    In fact this is now probably my most researched subject, with many outside sources cited here. As well I have received emails from outside the aquarium community from medical researchers congratulating my conclusions as to Redox by citing current research and then applying it to aquariums.

    Unfortunately many otherwise experienced aquarists in their writings or anecdotal forum comments (such as Aquatic Community & even the otherwise excellent but misinformed Barr Report) fail to look at the research that has gone on the subject of Redox and stick to their old tired theories about Aquarium Chemistry and the affect of Redox thereon much the same way many continued to claim the "earth was flat" even when proven incorrect.

    It is important to note, that just because many aquatic articles report only the importance of an oxidizing Redox, this does not make it true, science is not a vote!. It really is not that difficult to read outside (non aquarium hobby) articles that show otherwise. This is an unfortunate side of the aquarium hobby is that many will pass around old tired so-called facts as truths without reading anything that contradicts there theories masquerading as fact.

    I read a recent article that is easily found in search that is admittedly well written dealing with Aquarium Redox, with a good explanation as to what Redox is and more, however this article still chooses to repeat much of the same tired old information about only the positives of the oxidative side of the Redox equation, missing the evidence that the reduction side is also VERY important to a healthy Aquarium Redox Balance (I noted that the sources this particular article sited were all more than 15 years old which may explain much of the out of date information).
    Ignoring both sides of this equation is akin to acknowledging the importance of oxidation in the breakdown of dead animal and plant material, yet to ignore the fact that if this oxidation process were to continue unabated without reduction, we and all other living organisms would be consumed immediately!! This simple but important point must be understood.

    The basics of Redox are really not that hard to understand and are easily applied; that is knowing that a high bio load can have a downward effect on a good Redox while water changes, additional mineralization, UV Sterilization and more can have positive effect on Redox.
    Simply put, think of a Redox Balance of a magnet with opposite poles, and with without this electromagnetism of the water which makes up 90% of living tissue, the health of any living organism be it a fish, or aquatic plant will be affected!
    You must realize that these electrons necessary for balancing Redox are often used up and the assumptions often made about GH, UV Sterilization simply do not fit the evidence!
    I will also note, the more complex aspect/equations of Redox are certainly worth learning (I am still trying to “grasp” them all, however I would not let it frustrate you if they are difficult to understand.

    Finally; achieving a Redox of about +300 to -100 mV for marine or +125 to -200 mV for freshwater are the raw numbers we are aiming for, however if you have read this article thoroughly including the outside links/website other than my material, you will know that this is an extreme over simplification as there are times for higher and lower Redox readings!
    In other words, think of your Redox as constantly in flux with there certainly being times for a high/oxidizing Redox, but a +350 or higher Redox should not be the norm for most healthy aquariums or ponds.
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    For further information about WHY YOU SHOULD USE A UV STERILIZER

    Credit for some of this information:

    Another good article about this subject that I found is this: ORP and the Reef Aquarium

    Here is a quote from the above article; “Many aquarists have been lead to believe that ORP is a measure of water quality or purity. Manufacturers selling ozonizers and other oxidizers (like permanganate) have been especially keen to present that idea. But is it really true? Is a higher Redox indicative of "purer water" even when that Redox is manipulated artificially by adding strong oxidizers? Or is such an addition analogous to an air freshener that masks odors? I don't know the answer, but I think that aquarists should ask the question, and hope to hear useful answers before adding such materials to their aquaria.”

    This statement is where many aquarists have gone wrong in my opinion, A positive Redox is NOT a measure of water quality, but at least a Reducing Redox has more potential for a healthy aquarium.

    More Resources/references:
    (These are MUST reads in my opinion)

    Water Information & Conductivity An excellent read!
    Redox and Electrochemistry
    What is Mineral Redox Water?
    UNL Redox Biology Center
    Which way does Electricity REALLY flow?
    The Megahealth Society
    Positive & Negative Ions
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