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How to Oxygenate a Pond

Oxygen is essential to all life in the pond especially fish. Oxygen will always exist in a pond but it can disappear very quickly in summer. Here are some ideas to introduce more air into your pond

16 July 2020
How to Oxygenate a Pond

Adding oxygen to a fishpond is very important to fish health. This is particularly true in summer months and if the pond is heavily stocked. But even in ponds without fish an air pump will help keep the water fresh - particularly if a waterfall or fountain is not present. 

If you see any of the following signs, your pond will need extra oxygen:

  • Fish gasping at the surface of the pond or at any entry points for water (Waterfalls, fountains, streams).
  • Foul odours - decaying organic matter (Fish waste, plants, sludge) can indicate that there is a lack of oxygen, water movement or filtration.
  • Rapid algae development - This can be a sign of poor aeration and filtration.

Even if you do not have any of the above symptoms indicating a lack of oxygen, having an extra source of oxygen on your pond is extremely useful for the benefit of the pond! Having more oxygen in your pond provides the following:

  • A fantastic environment for your fish; the oxygen helps to reduce the chances of fish falling prey to various fish diseases.
  • The oxygen helps to encourage the development of beneficial bacteria in your pond; this bacteria will reduce the build up of sludge in your pond which in turn reduces the build up of various chemicals AND algae, keeping your pond free from algae!
  • During winter, when pumps and filters are normally removed from the pond, debris such as falling leaves can fall into the pond and fall to the bottom of your pond. Having an aerator on your pond helps the debris to decay safely via healthy bacteria.
  • Having an air pump on your pond during winter helps to add oxygen to the pond; but the ripples from the released oxygen can break the surface of the pond and prevent it from freezing over, which is extremely important for your pond.

If your pond is deeper than 3m, you will most certainly need an air pump or plants at the bottom of your pond. If you don't, then anaerobic bacteria will develop amongst the sludge at the bottom of your pond. This increases the likelihood of problems with hydrogen sulfide in your pond (this can cause an eggy smell near your pond).

Air Pumps

An air pump is a no-nonsense form of aeration that simply injects a stream of air into the water.  This air-stream is diffused where it enters the pond water (near the floor if possible) by an air-stone. The air-stone forces the air into multitudes of tiny bubbles so it is more readily dissolved into the water. Simple air pumps are inexpensive but the unit itself must be kept dry (typically the unit would be housed in a garage or out-building with the air-hose running outdoors). All-weather air pumps are more powerful, offer quiet operation and can be left outdoors. Another very popular approach is that offered by solar air pumps – these are lower power but need no wiring-up, can be left outdoors and work when the sun is out – just when the pond needs more oxygen. You can find our air pump range here.


There are many types of diffusers on the market and they are the most effaced form of mechanical aeration.  Air bubbles are passed through the water releasing oxygen as they go.  Look for diffusers that produce large numbers of fine bubbles which will be far more efficient.  Large bubbles may look better, but a stream of few large bubbles will have a smaller contact areas with the water.  Air-stones can also be used with a diffuser, or pump and venturi.

Oxygenator Plants

Oxygenators are submerged plants are positioned on the pond bed.  Most remain completely submerged although a few do produce flowers that peep through the water surface.  These are fast growers and breathe vast levels of oxygen into the water during the day. 

However the irony is that while they produce oxygen in the day they consume it at night, exuding carbon dioxide. The oxygen levels of a pond may drop overnight if the oxygenator plants are allowed too much space; they can overwhelm and smother a pond.

You can read all about the different plants we sell on our blog post.

Fountains and Falls

Oxygen enters the pond anywhere the water is in contact with the air.  Increasing the surface area naturally raises the amount of oxygen in the pond and that – by disturbing the water surface and creating ripples is exactly what fountains and waterfalls do.  As such, they serve both a decorative and functional role in a pond disturbing the water to keep oxygen circulating and prevent stagnation and the growth of the dreaded blanketweed. You can find our full range of waterfalls using this link and our range of fountain pumps here.

When building a waterfall or stream the flow rate of the pump is vital as this will dictate the effect of the feature being created.

  • For each 10cm width of waterfall or stream you will need 1000 litres per hour at the starting or top point of the feature.
  • For every metre above the surface of your pond, you will need 1000 litres per hour.

Therefore if the waterfall or stream is 50cm wide and 1m above the pond surface, it needs to have a pump that can push at least 6000 lph flowing over the start to ensure the feature looks good and has the desired effect.

Most pumps follow the same flow rate loss per height curve, i.e. at 0m head height the flow is generally the size of the pump, at 1m head height the flow is slightly less, at 2m the flow is reduced by more up to the max heads height which is where the flow rate is 0 lph and therefore the water will just not flow. 

One last point to mention is if the waterfall is being built from scratch and is not part of a pond then a header pool and a bottom reservoir may need to be built to ensure there is sufficient water to run the feature. A stream may require the same construction if it is not part of pond.

What size Air Pump should I get for my pond?

We have included a table below as a buying guide. Many pondkeepers do not keep fish in the pond and the adddition of a smaller air pump will be sufficient. Fish ponds require a larger amount of air, Koi ponds especially. If keeping other 'oxygen hungry' species such as sturgeon then the flow suggested below should be amplified further.

Please treat this as advice only - every pond is different. 

Output of Air

(litres per hour)

No Fish

(litres of water in the pond)


(litres of water in the pond)


(litres of water in the pond)

210 1500 1100 500
450 3000 2500 1200
600 4250 3300 1650
1200 8500 6600 3300
1800 12750 10000 5000
2400 17000 13200 6600
3600 25500 20000 10000
4800 34000 26400 13200
6000 43200 33000 16500

As always, if you have any queries please contact us using our contact details.

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