Pond Oxydator: how it works, dosage, and when to use it

A small ceramic pot placed at the bottom of the pond, without a cable or hose, releasing fine oxygen bubbles day and night: the oxydator often intrigues pond owners. Is it a gadget, an alternative to an air pump, or a water treatment? An oxydator is a slow-release active oxygen diffuser: it gradually breaks down a hydrogen peroxide solution into oxygen and water, without electricity, but in modest quantities compared with mechanical aeration. Properly understood, it is a useful supplement in certain specific cases. Misunderstood, it creates a false sense of security. Here is how it works and when it has a place.

How an oxydator works

The oxydator was popularized by the German manufacturer Söchting, and the principle has remained the same: a porous ceramic container, closed with a lid, into which a hydrogen peroxide solution (oxygenated water) is poured. A catalyst is located at the bottom of the container.

1. Hydrogen peroxide (H₂O₂) comes into contact with the catalyst.
2. The catalyst accelerates its decomposition into water (H₂O) and oxygen (O₂).
3. Oxygen escapes in the form of very fine bubbles and diffuses into the pond water, with a small fraction of peroxide passing through the ceramic.
4. The process continues slowly until the solution is depleted, generally over several weeks.

The decomposition rate depends mainly on temperature: the warmer the water, the faster the reaction, and the more frequently it must be refilled. It is a passive system, with no moving parts, no electricity, and completely silent.

It should be clearly distinguished from two other products that sometimes have similar names:

What effects does it have on the water

The effects attributed to the oxydator fall into three categories. They should be presented honestly, with their limitations.

An oxygen supply. Real, but modest. The amount of oxygen released by an oxydator is small compared with that supplied by an air pump or a waterfall, which continuously renew the air-water interface. The oxydator is useful for maintaining a slight continuous supply, especially in a calm area or at night, but not for oxygenating a densely populated pond on its own.

An oxidizing action. Active oxygen and the small fraction of diffused peroxide oxidize some of the dissolved organic matter and deposits. Users often report fresher water, fewer odors, and fewer organic deposits around the device. This effect remains local and gradual.

An effect on algae and germs. Manufacturers highlight a limiting effect on algae and germs. In practice, the oxydator can contribute to balance, but it does not replace properly sized filtration, UV-C, or nutrient reduction (feeding, leaves, sludge). An oxydator is not a remedy for established green water: it is an auxiliary treatment that acts slowly in an already balanced pond.

Water biology follows simple rules, well described in aquaculture water quality literature: dissolved oxygen depends mainly on temperature, photosynthesis, organism respiration, and exchanges with the air. These are the factors to act on first.

Choose the size

Oxydators are available in several sizes, from small aquarium models to models for garden ponds. Each manufacturer specifies a maximum water volume and an associated solution concentration for each model. The rule is simple:

• Respect the volume indicated by the manufacturer for the selected model.
• Beyond that, use multiple devices rather than increasing the concentration: two devices distributed throughout the pond are better than a single overloaded one.
• Take the pond's load into account: a very heavily stocked pond or one with a high level of organic matter consumes more oxygen; the Oxydator will only provide supplementary support.
• Place it in the right location: at the bottom or halfway down, in an accessible area for refilling, away from the pump's direct intake and areas where fish dig around frequently.

Dosage and refilling

Dosage for an Oxydator primarily means using the solution specified by the manufacturer. The concentrations used for pond models are significantly higher than pharmaceutical hydrogen peroxide, and both the ceramic and the catalyst are designed for them.

The refill frequency varies according to the water temperature and the model: as a general guide, every few weeks in summer and significantly longer in winter. The simplest approach is to note the date of each refill and check the level whenever you service the filter.

Oxydator or air pump

This is the question we are asked most often. The two devices do not serve the same purpose.

In a koi pond, the air pump remains the basic equipment. The oxydator can be added as a supplement, not used as a replacement. In a small patio pond without an electrical outlet, or in a plant tank with a few goldfish, an oxydator can instead be a practical and quiet solution.

Our guide to oxygenating pond water covers mechanical solutions, while the article on oxygenating a pond without a pump details natural alternatives. For a koi pond, also see how to choose an oxygenator for koi carp.

In winter

Winter is one of the seasons when the oxydator proves its value. When the water is cold:

• The solution breaks down slowly: one refill lasts much longer.
• The device does not need electricity and is not at risk of freezing at the bottom of the pond, as long as it remains under liquid water.
• It provides oxygen without stirring the water, so it does not mix the warmer deep layer where the fish stay with the cold surface layer.

But one important limitation remains: under a complete layer of ice, gases produced by decomposition (carbon dioxide and others) can no longer escape. The oxydator does not change this. An opening must still be kept in the ice, using a floating de-icer, a small air pump with the diffuser placed at a shallow depth, or a frost-protection heater.

Common mistakes with an oxydator. At the counter, we see the same situations recurring:

• Rely on the oxydator to “save” an overstocked pond or water that smells of mud, when the problem comes from the organic load.
• Forget about it for months: when empty, it is no longer useful, and no one notices.
• Place it directly in front of the pump intake, where the small amount of oxygen released goes straight into the filter.
• Increase the solution's concentration to “go faster,” risking damage to the ceramic and releasing too much peroxide near the fish.
• Turn off the air pump in winter because an oxydator is installed, without keeping an opening in the ice.

When used properly, that is, as a discreet supplement in a pond whose filtration, aeration, and fish load are already under control, the oxydator is genuinely useful. Used as a miracle solution, it disappoints.

Safety

The hydrogen peroxide solution used in pond oxydators is a concentrated product. It requires the same precautions as a corrosive cleaning product:

• Wear gloves and goggles when filling: the solution strongly irritates the skin and especially the eyes. In case of splashes, rinse thoroughly with clean water and seek medical advice if necessary.
• Keep out of reach of children and animals, in its original labeled packaging.
• Keep cool and protected from light: peroxide decomposes with heat and produces gas. The caps are often designed to allow this gas to escape; do not replace them with an airtight cap.
• Never mix with other treatment products, especially those containing chlorine or permanganate.
• Fill away from the water, on a stable surface, avoiding any overflow into the pond.

Common case: a 3 m³ pond with a few goldfish, no electricity at the bottom of the garden. In summer, the water becomes stagnant and the fish come to breathe at the surface in the early morning. An oxydator sized for this volume provides a continuous boost, but the real solution also involves feeding less, removing leaves, and providing some shade. During a heatwave, emergency liquid oxygen can help get through the critical period while waiting to restore the balance.

Read also

For occasional active oxygen treatments: Understanding and using active oxygen for a healthy pond.

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Frequently asked questions

— How does an Oxydator work?

A catalyst placed in a ceramic container slowly breaks down a hydrogen peroxide solution into oxygen and water, which diffuse into the pond over several weeks, without electricity.

— Does an Oxydator replace an air pump?

No. It provides little oxygen and does not promote gas exchange. In a koi pond or a heavily stocked pond, the air pump remains essential; the Oxydator is only a supplement.

— Can an Oxydator be filled with pharmacy-grade hydrogen peroxide?

It is recommended to use only the solution intended by the manufacturer for the model concerned, whose concentration is adapted to the ceramic and catalyst.

— Can an Oxydator be used in winter?

Yes, it works more slowly and a refill lasts longer. However, an opening must be kept in the ice to allow gases to escape.

In summary

• The Oxydator slowly breaks down hydrogen peroxide into oxygen and water, without electricity.
• Its oxygen contribution is real but modest; its oxidizing action is gentle and local.
• Use the volume and solution specified by the manufacturer, and add more devices if needed.
• It complements an air pump without replacing it, especially in a koi pond.
• Concentrated solution: gloves, goggles, cool storage, and keep out of reach of children.

Last updated: October 3, 2026.