Tag Archives: fish health


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 4/1/22

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 AAP Wonder Shell bandwagon selling clearance Wonder Shells [as a the genuine product is one of the best methods to provide mineral Cations to help with Redox balance], 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 by Carl Strohmeyer based on his decades of experience in professional fishkeeping [including help from other prominent fishkeepers such as Rogier Fentener van Vlissingen].

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: Hanna Professional Waterproof Portable pH/ORP Meter

Further Reference:
Magnetically Charged Water

The author at Aquariumscience.org makes several mistakes starting with the typical liberal Ad Hominem argument, which a full reading can easily dispute in his attacks upon the author of the highly regarded “Aquarium Redox” article referenced here and found on the AAP Aquarium Information website.
With just a little research on his part, he would easily see that the website selling was put up AFTER the information website (& only after many asked for him to sell products his experience suggested as noted on his aquarium keeping bio webpage).
As well some of the products recommended, such as the Redox Test Meter are not sold by AAP and the link is to an outside source with no affiliation whatsoever (including no “kick back” like Amazon affiliates get).

He does not even know the ingredients of an AAP Wonder Shell and simply assumes that it has Sodium Thiosulfate (which it has none and a little research that he claims to make would find this on the selling website).
He also misses what products are promoted based their [proven effectiveness and the FACT that a Fresh Wonder Shell much more quickly removes oxidizers than an old, less fresh since these Cations do indeed slowly “go away” just like an open soda slowly loses its fizz.
Sadly this rather vile attack clearly shows he know nothing of the author and his background, including the 1000s of hours he has given back to the aquarium keeping community over his decades in it all the while only earning less than minimum wage from the website that displays these articles.

In looking at this attack article on Aquariumscience.org, it is clear he is the one who asks persons to trust him based on his education in chemistry, despite no professional experience and zero reference links. Yes his articles make some good points, he does not go into real in depth explanations and at the end of every article asks readers to trust him based on his education.
It is noteworthy that his article on bacterial diseases, he misses the 75% of the cure for Columnaris is prevention and good aquarium husbandry, NOT the purchase of medications, despite his Ad Hominem attacks on AAP for selling product even though their article provides this information. He even gets the more effective medications wrong, showing his lack of real experience in aquarium keeping [it seems he misses that while a degree in chemistry is certainly helpful, it does not make up for experience in keeping 1000s of aquarium professionally for decades and the fact the author of the AAP article has been sought out by industry insiders for his help when it comes to aquarium disease prevention].


* 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 2022, By Steven Allen



Copyright 2014, By Steve A
Revised 10-18-19

I am using this article for the first “aquarium article digest” entry as this seems to be an area of aquarium/pond keeping with MUCH misunderstanding, and even as of the most recent revisions, continues to be if not more so than when I first wrote this article in 2009.

Ultra violet ‘C’ sterilization is a process that is one of the most effective means of disease prevention in aquariums and ponds and for general water quality control in aquariums and ponds.
A correctly installed, quality UV Sterilizer helps provide and improve a fish’ chances in fighting difficult diseases such as ich even though UV Sterilization is less effective directly in destroying this disease pathogen.
See this example of an online seller of good to premium quality Sterilizers: Aquarium & Pond UV Sterilizer

Aquarium UV Sterilizer Clears OxidizerPart of the reason for aid in fish immunity, is that UV Sterilization is that the UVC irradiation which is contained in the unit will break down oxidizers in the water column that would otherwise lower a fish’ immunity (Redox Balance), this aspect is often missed as many persons use only focus on the germicidal/algacidal properties of UV Sterilizers.

This not only has been proven in controlled tests by gurus in aquarium research such as Carl Strohmeyer, it is easy to demonstrate by adding an oxidizer such as Potassium Permanganate that colors the water and running a level one UV sterilizer against a control aquarium with none (all parameters, bio load, etc. otherwise equal) and noting the considerable speed the Potassium Permanganate is cleared from the aquarium utilizing the UV Sterilizer.

The photo to the above/right demonstrates this.
Credit: Aquarium & Pond UV Sterilization | How to use a UVC Sterilizer

Further Reference: Aquarium Redox Balance

Please read this article for more about this subject:
“Fish Immune System and UV Sterilization”.

Unfortunately many aquarium/pond forums also focus only on the aspect of irradiation of disease (which can be hit or miss depending upon installation and UV quality), but miss the aid UV Sterilizer provide in improving Redox balance.
Many of my friends in the professional aquarium & pond maintenance business have cited many times that a new customer would call them out for help complaining the UV Sterilizer they purchased elsewhere was useless, but after investigating these professionals would find that the UV was of poor quality and/or incorrectly installed.

This has been especially common of late with the influx of low quality UVs such as the Green Killing Machine, Submariner, Jebo, AquaTop, and many others which is what you get for under $50 on eBay or Amazon, as well as some of the many low end online retailers.

The unfortunate aspect of purchasing these low end UV Sterilizer is that these are not really sterilizers at all, rather just clarifiers.

So what often happens is a person purchases one of the cheap UV units, then sees no improvement in fish health, then goes onto some aquarium forum, Facebook, Youtube, Yahoo Answers, etc. and reports that the device was useless.
The problem is the devise they purchased was useless for true level one UV Sterilization, but the process and the concept is not.
This very common problem is analogous to purchasing a thin plastic tarp to cover ones swimming pool and then when a child still falls in, stating pool covers are junk, when in fact a pool cover designed for protecting children from the pool should have been used and would have worked!!
Example: http://www.poolcoversinc.com/benefits.shtml

Excellent video on the subject:
Do I really need a uv sterilizer
Do I Really Need UVC?

What are we looking for to properly utilize UVC energy for irradiation?

  • Water flow rate through the UV Sterilizer. This is often expressed as “gallons per hour” or gph per watt of UVC energy
  • Dwell time (related to flow rate). This is the time the water stays inside the UVC irradiation chamber
  • An actual High Output (HO) low pressure UV Lamp/Bulb. The difference between the more commonly used medium pressure UV lamps is as much as FOUR TIMES the UVC output. Even in a less expensive Chinese built UV Sterilizer this can mean the difference between a TRUE UV Sterilizer and a UV Clarifier.
    Most sold via Amazon and other discounters DO NOT utilize HO UV lamps.
    Further Reading: Actual UV-C Emission from a UV Bulb; Aquarium or Pond
  • Water Turnover in pond or aquarium per hour. This is how many times per hour the water is passed through the UV Sterilizer as per a given unit of water in the aquarium or pond
  • Distance of UV Lamp from UV Sterilizer containment ‘wall’. This should be no more than 3 mm, which many “built in” canister aquarium or pressurized pond UVs are much greater than.
  • Temperature of water. UVC is effective is between 20 C (68 F) and 40 C (104 F)
  • Pre-Filtration including Turbidity of water. Particulates in the water can & do have a affect the ability of the UVC to damage or destroy pathogen, algae, or reduce oxidizers (Redox)


There is a lot of new evidence as to the benefits of UV sterilization for ALL fish, and many myths have been dispelled such as “UV Sterilizers destroying beneficial nitrifying bacteria”.
I will try and present material in as readable a format as possible, rather than get down to too much scientific jargon that is difficult for many to understand as many facts can often be presented without every technical term applied.

UV Sterilization is also effective for controlling suspended algae (green water) in ponds, along with proper filtration such as Veggie Filters/pressurize filters, please see this article:
“A Clear Pond; pond information”.

True Level One UVs are also useful in Reef aquaria, especially new ones where the chance of disease introduction is high, as well the UVs help in keeping a balanced Redox Potential which is useful for disease prevention via boosting the fish’ own immune response.
As the reef aquaria ages the sterilizer can be placed on a timer or turned on and off as needed (although I still recommend running 24/7 in many reef aquariums).

As for the Redox Balance, this is an often overlooked aspect of both freshwater and saltwater aquarists that HAS BEEN PROVEN in well funded studies to aid in immune response.
Unfortunately some aquarium forums choose to ignore this science or push low end UVs (often under $50) that cannot product level 1 UVC

The Redox Balance is basically the oxidation and reduction properties of water.
This is VERY important for proper breakdown of organic waste (the oxidation side of Redox)! Especially in aquariums where the fish/invertebrates come from waters of low turbidity (African Cichlids) or tend to produce a lot of waste (Goldfish).
“Most experts now agree that the Redox should be +300 to -100 mV for marine or +125 to -200 mV for freshwater for healthy fish immunity, which a UV Sterilizer can help maintain.”
Used with permission From: “Aquarium & Pond UV Sterilization

For more information about the Redox Potential, please reference:
Aquarium Redox Balance

Further Reference: UV Therapy

Anecdotal Arguments Against

One argument against UV Sterilizers in ponds is that they are not natural, but for the clarity most persons want out of their pond, this is not possible without either UV sterilization or a flow thru stream (although many persons with well planted, well shaded ponds do well with clarity too, but UV Sterilization further compliments these ponds too).

Many articles I have read state that a UV is not that beneficial to an established aquarium as a healthy aquarium depends on beneficial bacteria typically growing on media in your filter which neutralize ammonia.
Unfortunately the problem with this statement is beneficial bacteria belongs in the filter, not in the open water column which is all a UV Sterilizer effects.
Also this may work well for some advanced aquarists who are not adding fish and have a healthy Redox Potential/Balance, but not in the real world of average and above average aquarists that I and many of my friends have dealt with in the 100s of aquariums they have serviced.

Also it is noteworthy that an aquarium is a closed system, NOT OPEN, so inputs of added buffers, minerals, Redox reducers, etc are necessary.
The use of level 1 UVC irradiation is just one more of these inputs since Redox Balance has been scientifically proven to improve with the use of level 1 UVC.
The problem is often these persons stating they used a UV Sterilizer with no improvement in fish health, were likely not setting up the UV correctly or more likely, were using one of the many cheap UVs flooding the market such as the JBJ, AquaTop, Green Killing Machine from sellers such as Amazon.

Some Recommended Aquarium UV Sterilizers

  • AAP/TMC Vecton & Advantage Level 1 & 2 Capable UV Sterilizer
    There are simply NO BETTER UVs than these. TMC made a name for themselves with these decades ago and are still the best value (yes Aqua Ultraviolet & Emperor are also good, but these still fall short in dwell time and value
  • AAP Terminator UV Sterilizers
    While an economy UV sold under many names, these have a HO UVC Lamp that most other Economy UVs do not
  • AAP Submersible/Internal UV Pump/Filters
    While this style is not as efficient nor as long lived, it is very user friendly. Once again the AAP models is different than most in that it utilizes a HO UVC lamp along with adequate Pre-filtration that most others do not

Aqua UV versus TMC UV Sterilizer
Aqua Pond UV vs TMC AAP Pond UV Clarifier Sterilizer


UV Sterilizer maintenance is quite straight forward; make sure you keep your unit dry on the outside, if used for a pond try and protect your unit from harsh weather (most sterilizer can withstand the outdoor environment, they just last long if they can at least be partially sheltered).

Change your UV bulb every 6 months for aquariums, and also every 6 months for ponds in warm climates where there is no winter freeze.
In cool climates a pond UV bulb can be changed every season (usually late spring/ early summer).
See: High Output UVC Replacement Lamps

For a full in depth article on this subject:

How UV Sterilization Works, For True Level 1 or 2 in Aquarium/Pond

The above article should be read for much better understanding of how to correctly use your UV Sterilizer.

Unfortunately with the Google Search of late mostly becoming a Spam search for about.com (not “the spruce”), Amazon.com and others; GOOD RESEARCHED articles such as the one above are more difficult to find, but I urge my readers to read this article in full, then read it again (and maybe again until you understand the concepts presented!!
Do NOT purchase a UV Sterilizer UNTIL you read the above article

If you do decide to purchase a decent UV, not just some cheap toy calling itself a UV Sterilizer, consider this website that a professional in the industry I know with 3.5 decades of experience in UV Sterilization owns:
Good to Premium UV Sterilizers for Aquarium or Pond


*Aquarium Lighting
An in depth article that I have found to be the most accurate and up to date anywhere. It includes information about the growing in popularity LED Aquarium Lights.

*A Healthy Aquarium, Disease Prevention
An excellent step by step scientifically tested/proven method to keep a more disease free aquarium

*Aquarium Ich: Ichthyophthirius Multifilis and Cryptocaryon Irritans

*FISH COLUMNARIS | Fungus & Saprolegnia | Treatment & Prevention

*Pond Algae

*Pond Care, Information

Copyright 2019, By Steve Allen