Local Call Number: 087 354 1288 | JHB: +27 (0) 11791 4403


Ozone in Koi Ponds is used to maintain clean healthy water for the koi and aquarium fish to live in safely and healthily

Frequently Asked Questions.

  1. What is Ozone?

Ozone gas occurs naturally in the atmosphere. When a molecule of Oxygen, O2, is bound to a third oxygen atom, it becomes Ozone, or 03. Ozone is an unstable bluish water-soluble gas with a characteristic smell. At low levels it makes the air smell fresh and its colour makes the sky blue. Ozone is the 2nd strongest known oxidiser and the most powerful readily available water sanitiser. It kills bacteria and viruses over 3,000 times faster and is a 50% stronger oxidiser than chlorine. It is unsurpassed for control of many types of common bacteria such as E. Coli and faecal coliforms as well as the deactivation of virus, fungus, mould, mildew and cysts, and is not carcinogenic.

  1. How does it Work

Ozone is nature’s way of purifying the air we breathe. As ozone circulates and comes into contact with airborne pathogens, one of the three oxygen atoms detaches itself from the Ozone molecule, attaches itself to the pollutant and oxidises it and turns it into a safer compound. Ozone is nature’s way of cleaning our environment.

Ozone is such a strong germicide that only a few micrograms per litre are required to demonstrate germicidal action; it destroys all pathogenic and saprophytic microbes in water. Factors like humidity, temperature, pH, Ozone concentration levels, type of organism and contact time, will affect the kill rate for pathogens, but the action of Ozone gas in water is instantaneous and after oxidation, Ozone returns to its original form of Oxygen, without leaving any toxic by-products or residues. Ozone is a natural disinfectant and steriliser and unlike chlorine, it does not produce trihalomethanes or chloroforms in water and so leaves no harmful toxins or residues in the water.Without dispute, scientifically speaking, ozone is the most effective natural bactericide and viricide of all the disinfecting agents.

  1. How do we measure the levels of Ozone in the pond water?

The Ozone dosing of water is measured in millivolt terms and is expressed as the REDOX or ORP level (Reduction/Oxidation potential) of the water. Normal pond water will have a REDOX level of around 200 mv or less. Sterile water has a REDOX level of around 700mv. Some Ozone generators are designed to automatically regulate the ozone dosing to keep the REDOX level at a preset level, normally around 350mv – 380mv in a healthy aquatic environment, so that the water is not sterile or anything like, since it could not then support life.

  1. What is a Redox reaction?

A chemical reaction in which electrons are removed from one atom (which is thereby oxidised) and added to another (which is thereby reduced). The movement of electrons is then measured on a millivolt scale.

  1. What is Oxidation?

Oxidation is the process that causes steel and iron to rust, an apple to shrivel and go brown once cut open and is also responsible for the degeneration or ‘rusting’ of our bodies, causing cellular breakdown. Oxidisation or oxidative stress has been linked to many degenerative and chronic diseases including heart disease and cancer. It is also responsible for premature ageing. Oxidation permanently disrupts and damages cell structure, thereby killing simple cellular organisms very quickly. Our beneficial nitrifying bacteria employ the process of oxidation to remove harmful ammonia and nitrite from our pond water by converting Ammonia to Nitrite and then Nitrite to Nitrate.

  1. What causes Oxidation?

Oxidation is caused by oxygen molecules that are missing an electron, making them unstable. Oxygen cannot exist in this unstable form and has to be stabilised. The molecules collide with healthy, stable molecules be they in metal, or living cells and then ‘steal’ an electron in order to stabilise themselves. This damages and de-stabilises the molecule that they have collided with leaving it now missing an electron itself. The formally healthy molecule is now itself an unstable ‘free radical’ and will also try to stabilise itself by colliding with another healthy molecule and stealing one of its electrons. This creates a knock- on effect that damages and destroys living cellular structure, and in our pond environment this includes parasites, viruses, bacteria, algae or any other living organism with a simple cellular structure.

  1. If Ozone kills bacteria, what about my Bio-Filter – won’t that be affected?

Yes – but only beneficially! Pathogens are killed instantly as they pass through the Ozone stream in the Ozone reactor or protein skimmer, but obviously you’re nitrosomonas and nitrobacter do not, as they live on your filter media. True, they are free swimming as well, and any that pass through the Ozone system will be zapped. However, it is a recognised and fact that the beneficial filter bacteria have relatively short lives but multiply very quickly. Further it has been scientifically proven that nitrification bacteria will die faster without the presence of Ozone than with Ozone. This is almost certainly because the entire pond environment is cleaner and considerably more aerobic (oxygen rich) in an Ozone treated pond, and it is a well known fact that nitrifying bacteria reproduce and perform much better in oxygen rich systems. Many pathogens, on the other hand are anaerobic (live in a zero or reduced oxygen environment) and in a pond treated with Ozone there will be virtually no chance of anaerobic conditions existing. So the high Redox levels of the pond water is of considerable benefit to our friendly bacteria, but is definitely the enemy of pathogens.

  1. If the Ozone kills only on direct contact in the Ozone reactor – what kills Algae and other organics that don’t pass through the Ozone stream?

Ozone raises the Redox potential of the water substantially. This renders bacteria, algal spores and other organics much more susceptible to oxidation – to having their cells destroyed or disrupted, even though they are not necessarily in direct contact with Ozone. Put another way, chemically the pond water is far more reactive as it is saturated with Oxygen, and single cell organisms or organisms with a simple cellular structure are easily oxidised and therefore tend to have a shorter life span. Direct contact with Ozone in the Ozone reactor means instant death, the higher Redox of the pond water means cells are easily oxidised (killed) and cannot reproduce effectively so their population decreases.

  1. I’ve been told that Ozone makes the water sterile and can mean that the koi’s immune system deteriorates as it doesn’t have to work so hard any more?

This is simply not true! In a sterile pond environment, the Redox level is around 700mv – at this level all life would cease to exist in the pond. Koi ponds usually run at a Redox level of around 350 – 400mv. At this level the majority of pathogens are destroyed but your koi will be very happy and healthy. Also there is absolutely no scientific evidence that disinfection of pond water by oxidation, whether this be by Ozonisation or chemical additives affects the immune systems of fish, including koi. In their natural state, in rivers or lakes, each fish has a comparatively massive volume of water in which to live and the bacterial loading is much lower than in a man made koi pond. Using Ozone simply helps us reproduce nature. It is like attaching your pond to a freshwater stream, with new water flowing in on one side, and old flowing out of the other – effectively continually flushing out the system. Would a koi’s immune system weaken in nature because it is not continually subjected to high bacteria counts? Of course not – quite the reverse!

  1. Can I use an Ozone system in place of a conventional filter?

No, you should consider an Ozone system to be a part of your overall filtration strategy, as it will not replace either the mechanical or biological elements of your conventional filter, but it will enhance the performance of your existing system thus rendering it far more efficient.

  1. Can I still treat my pond with chemicals? and what happens when I do?

Yes of course, from time to time you may need to use a pond medication for parasites etc. When you do, simply switch off your Ozone generator. Ozone would destroy chemicals in the pond very quickly and would render your treatment useless. When your treatment is complete, switch on again and the Ozone will clear the chemical residue very quickly.

  1. I have heard that Ozone is dangerous to human health – is this true?

Ozone is a powerful oxidising agent, and certainly if used carelessly or incorrectly it could be dangerous to health. However the same is true of almost all the chemicals we use in our hobby. Potassium Permanganate and Chloramine T are powerful oxidising agents and need to be handled and used correctly and definitely not ingested. Similarly Malachite Green, and Mercurochrome are dangerous substances which should not be handled with bare hands. Of course we know this and treat these substances with the respect they deserve. Indeed none of the substances we use in our day to day koi hobby should be ingested, inhaled or come in to contact with bare skin – again common sense. Similarly we certainly don’t want to breath in Ozone constantly as it can irritate the respiratory system, and therefore Ozone systems must be specified and installed correctly, with any residual Ozone produced gassing off to atmosphere – not inside your filter house! This is common sense, just as we should always install residual current circuit breaker devices in our electrical circuits anywhere near water – to prevent any chance of electricity and water mixing – which would almost certainly have fatal consequences.

Yet we frequently hear from people who seem to have an inbuilt fear of ‘new’ technology, or simply because they don’t understand even the basics of how Ozone systems work, that they must be ‘dangerous’ and should be avoided.

Ozone has been in use as a safe and effective disinfectant for ventilation systems in offices, factories and even ocean going liners since the 2nd world war. It is most unlikely that such systems would have been developed or used if there had been an unacceptable health hazard. Ozone is used in many facets of industry, for many different industrial applications and to our knowledge no -one has ever died or been seriously injured as a result of Ozone poisoning!

Ozone has a very distinctive sharp, ‘fresh’ smell which many people identify with a disinfecting agent and it can be detected by the human nose at levels 10 – to 30 times lower than that which is recognised as being harmful to human health. In addition, Ozone is very unstable, and once created, immediately begins to decompose back to Oxygen again. This decomposition takes between a matter of several seconds and several minutes. It does not therefore even exist in a dangerous’ state for a significant time. We can therefore categorically state that a properly installed Ozone system would be a very safe part of your koi filtration system and one with which there would be no associated health risks whatsoever.

  1. Can I dispense with my UV system?

Theoretically , yes you can. However in practice we find it is best to leave the UV in place. This is because in most installations there is a much higher water flow through the UV than the Ozone reactor or protein skimmer. In summer the algae which causes green water can persist without a UV because Ozonisation improves water clarity dramatically and highly oxygenates the water. This provides the perfect environment for Algal growth and the use of a UV is of course beneficial. In addition, some Ozone generators have to be serviced from time to time and the UV can serve to keep the water clear whilst the Ozone system is switched off. We would recommend leaving your UV in place if you are using less than 1gm/hr Ozone per 5000 litres.

  1. Can I still use salt in my pond?

Yes, absolutely. The Ozone won’t affect the salt and you will find your protein skimmer produces a lot more foam with salt in the water, so it actually works even more efficiently.

  1. All sounds very complex – do I really need an Ozone system?

No, we can’t claim an Ozone system is an essential part of a koi pond system, but that’s what was said about bottom drains and vortexes a few years ago. Now very few ‘proper’ koi ponds are built without these essential items. For the serious koi keeper we would recommend an Ozone system be included as part of the overall filtration strategy. We believe that in the near future, Ozone systems will become just as much of a necessity as a bottom drain.

Koi are beautiful but expensive creatures and each year thousands of koi die needlessly from all kinds of illnesses most of which are simply caused by poor water quality – nothing more. In any koi pond one of the eternal and recurring problems that we have to overcome is bacterial disease and in a well stocked and mature koi pond the bacterial load on the system can become very high – especially in the summer months. Without doubt the single biggest benefit of installing an Ozone system is that the bacterial load on your system (and therefore on your koi) will be drastically reduced. Ergo less disease – more healthy koi. Unquestionably water quality will also be transformed using Ozone. Ask yourself why have marine/tropical aquarists been using Ozone to help manage water quality for the last 15 years or so? Why is the koi fraternity always the last to catch on? The saying that we are not koi keepers – we are water keepers is absolutely true. If your pond water quality is superb, your koi are more likely to be healthy and live longer – it’s as simple as that.

  1. What comprises a complete Ozone system?

We need several items to build a complete Ozone system, rather like building your own Hi-Fi system. First we must have an Ozone Generator to create the Ozone initially and optionally a Redox controller which enables the system to operate automatically and switch on and off the Ozone supply as required. We then need some kind of Protein Skimmer or Ozone reactor to mix the Ozone produced with the water as efficiently as possible, allow it do ‘disinfect’ the water, and then remove any residual Ozone before the water is returned to the pond. Using a good venturi does mix the gas with the water quite well and you could get away without a mixer by introducing the ozonised water after the venturi in to the bottom of a settling or final disinfection tank before it is released in to the main pond. Alternatively the ozone can be bubbled in to the disinfection tank using an aquarium air pump diffuser stone. If the main pond is long and thin, it is also possible to diffuse the ozone direct in to the main pond at the correct levels so that all wat er from the circulation system will pass through the ozone bubbles in the main pond. To obtain more ozone it would help to increase the ozone levels by using an air drier before the drier as Ozone generators produce more Ozone using dry air. Without a doubt, however it is of vital importance that the ozone gas is mixed properly with the water for optimum results.

It is important to match the Generator to the circulation and mixing system to achieve the desired result.

  1. The technology sounds complex, are these systems reliable?

Early Ozone generation equipment was not particularly reliable, as the generators produced a lot of heat, and early systems were water cooled. These were large and cumbersome and needed fairly regular maintenance. The latest systems (3rd generation) are all air cooled, are far more efficient and therefore produce less heat energy. The smaller systems use tiny amounts of electrical energy and are simple and very reliable devices which are guaranteed for one year. There are no moving parts in the generators and the only maintenance required is regular cleaning or changing of the air filter and cleaning of the generator electrodes. In the larger units which use cooling fans, filters and fans need to be services similair to a computer.

Also the Redox sensor should be cleaned with a soft toothbrush regularly to prevent it fouling.

  1. How do I choose the right system?

Firstly, you obviously need to know your pond capacity. From this you can first calculate the size of Ozone generator you will need by using the formulae of between 0.5gm/hour and 1gm/hour of Ozone for every 5000 litres. We suggest you email office@ozonize.co.za with the plan and details of your pond and equipment and we will then recommend a suitable system.

Close Menu