What does an air pump do?

An air pump works by pushing air out of a diffuser placed at the bottom of the pond, this produces bubbles which rise through the water and hit the surface. The bubbles themselves are passing through the water too quickly to diffuse any oxygen however the surface movement which is created allows for oxygen absorption. This also creates circulation drawing water from the base to the surface, constantly moving the dissolved oxygen throughout the pond. This circulation also assists in keeping the water clear as it keeps the waste particles in the water column, allowing the filtration to remove these.

Why should I use an air pump?

When it comes to looking after fish and aquatic life, whether marine, tropical or cold water there is one essential element to their survival, which is oxygen (O2).

Fish will extract oxygen from the water and expel carbon dioxide using their gills. Gills are an organ which consists of many small blood vessels, called capillaries and are located on the side of the fish’s head, behind the mouth. The water passes through the mouth of the fish and exits out the gills, this allows for the capillaries to absorb oxygen directly from the water into the bloodstream and is subsequently distributed around the body.

Oxygen is absorbed into the water through the atmosphere and disturbing the water surface increases the rate of which this process occurs. When water becomes stagnant oxygen is used up by bacteria and aquatic life gradually reducing the concentration, eventually reaching dangerous levels. The oxygen content within water is commonly around 8mg/L or 8 ppm which is minimal compared with the oxygen content in air, at 200,000ppm. Colder water is able to hold a higher volume of dissolved oxygen and warmer water will usually have reduced oxygen levels. However, this low concentration of oxygen requires fish to pass large volumes of water over the gills in order to extract sufficient oxygen for survival.

Which air pump do I choose?

When deciding upon which air pump is suitable for your pond the key areas to look at are how many diffusers will be used, the style of diffuser and the depth of the pond. A wide variety of diffusers are available, from balls to flat circular stones. The design of stone is mostly stylistic however each diffuser will allow differing volumes of air through, usually measured in litres per minute. This information is very useful in guiding the size of air pump required. The number of diffusers used subsequently affects the required power of the air pump, due to each stone needing its specified volume of air to be effective. Essentially this means the litres per minute for the diffuser is multiplied by the number of diffusers to result in overall volume, for instance, using 5 diffusers requiring 10 litres per minute will equate to an air pump which produces 50 litres per minute. Finally, the depth of pond will increase the pressure or resistance against the pump resulting in a lower volume of air being released from the diffuser, so it is important to account for reduction in this situation.

How do I set-up and air pump?

Once you have decided upon the style and number of diffusers and a suitably sized air pump it is straightforward to set up. The air pump will need to be plugged into a socket or wired into a switch box, and then placed somewhere which is flat, supports the air pump and will not become waterlogged. Air line will then be connected onto the port of the air pump at one end and the other connected to the diffuser. This diffuser can then be dropped into the pond. The placement of the diffuser does not matter too much as it will mostly be aesthetic although it will provide added benefits through water circulation if placed in an area of still water or into the deepest section of the pond. Dependant on the stone placement the style of air line will also change, if the diffuser is in the centre of the pond, then sinking air line would be best to use as most other airlines will float across the surface of the water. However, if just sitting at the edge, then the weight of the diffuser will allow the length of air line to run vertically down the side.


An air pump is not essential to all ponds however the benefits cannot be ignored. The addition will ultimately improve the health of the pond, creating a more suitable environment for all aquatic life whilst also assisting to manage the levels of waste. The movement of these bubbles can also be visually appealing and prove enjoyable for fish to play around in.

Thank you for taking the time to read this article, I hope that all aspects of this subject have been clarified. Although if you need further assistance with an air pump or any other pond equipment please refer to one of our other blogs, or get in contact with our experienced team who will be happy to share their knowledge and skills to improve your feature.

The Pond Guys are a pond installation and maintenance business based in Surrey, with teams covering London and the South East.

We are specialists in all types of ponds from ‘state of the art’ Koi ponds through to tranquil water gardens and water features.

Do get in contact for any help and advice, or indeed if you need help with any aspect of your pond or feature.

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