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How to Add Oxygen to a Garden Fish Pond Using an Air Pump and Air Stones

Waste builds up on a pond bottom. Oxygen is needed to break down this waste. Fish need oxygen just to survive. At night plants need to absorb oxygen from pond water. Most important of all the massive quantities of nitrosomonas and nitrobacter bacteria in every pond filter system need large quantities of oxygen to enable them to survive and remove pollutants from pond water. A great deal of the debris you see on the bottom of your pond starts life as a windborne bit of debris that for a while floats on the pond surface. If the debris is allowed to sink it becomes unsightly and if organic in nature it also consumes precious oxygen in a pond to be able to break down the organic waste.

In summer and on calm hot balmy days ponds with lots of fish may suffer from oxygen deficiency. The fish and other parts of the oxygen consuming systems are thus threatened by a lowering of levels of oxygen and when this is coupled to the fact that warm water can hold less oxygen than cold water the threat of fish stress and even death can become real.

Air contains about 20% oxygen with the rest being mainly nitrogen, carbon dioxide and small quantities of minor gases.

At higher altitudes water can hold even less oxygen than at sea level.

Why It's Easier To Keep Goldfish or Koi and More Difficult To Keep Trout In Ponds

Trout are fast moving predators and thus need lots of oxygen to keep their metabolism working. For this reason they prefer colder water (because cooler water holds more oxygen) fast moving rivers and streams in which the maximum amounts of oxygen can get transferred in the turbulent waters.

Koi and goldfish are members of the carp family and this type of fish prefer warmer (less oxygen dissolved in warmer waters) water. They are also grazers or bottom feeders and don't need the speed to catch food.

Avoid Fish Stress in Overcrowded Garden Ponds ... Use An Air Pump

An air pump is situated outside the pond. The air pump is then connected using small bore plastic tubing to a series of air stones (porous ceramic blocks in round or rectangular shape). The air pumped into these air stone becomes very diffused into tiny bubbles that rise to the surface of the pond ... as these air bubbles rise in contact with water some of the oxygen inside the bubble finds its way into the pond water and this process repeats itself continuously. As such the oxygen that is taken up by fish, plants, bacteria etc is replenished and all pond inhabitants remain happy and unstressed.

The Different Types of Air Pumps

The first thing to take into account is that high quality large koi pond air pumps are expensive because they need to deliver lots of air to significant pond depths. Most large koi ponds are at least 6 feet deep and adding air to water through porous air stones at this depth takes a lot of pushing. Air pumps are specified based on maximum depth to which they can pump and the volume they can deliver normally expressed as litres per hour (lph) or cubic metres per hour. Larger sized air pumps can also deliver through multi ports to differently located air stones.

Most air pumps need protection from the rain and severe weather so are bets kept in protected areas.

Bradshaws supply air pump models from Oase, Blagdon and Gardena. It's a case here of you get what you pay for so if your serious about fish keeping and you believe you'll benefit from adding air (and every pond will) then go for the best you can afford.

I would recommend the Blagdon Koi Air pump products. These come in 3 model sizes ...

  • Koi Air 25 ... air output is 1500 lph at a maximum depth of 2.2 metres and can supply up to 6 air stones

  • Koi Air 50 ... air output is 3000 lph at a maximum depth of 3.0 metres and can supply up to 12 air stones

  • Koi Air 65 ... air output is 3900 lph at a maximum depth of 3.5 metres and can supply up to 14 air stones

The Smart Solar Oxygenator

The Smart Solar Oxygenator is an ingenious air pump suitable for small to medium sized ponds, complete with 2 air stones. Working via solar power this air pump oxygenates pond water in sunny weather when oxygen levels are depleted. Powered and supplied with a separate solar panel. Simple to install, there are no wiring and no running costs.


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