How do I select the right pump for my garden pond?

A pond is essentially a small, enclosed body of water that is 'cut off' from the outside world. Although ponds are affected by the climate, falling leaves, dust, insects and many other factors, it lacks a numbr of important ingredients that most healthy, natural bodies of water psssess. These include a constant supply of fresh water, continual remaoval of 'old' water, a large bacterial population to process wastes and a food supply that is in balance with the pond inhabitants. 

If a garden pond can successfully reproduce its natural counterparts by being large enough and sparsely stocked with fish, and by containing abundant plant growth, then it will become self-sustaining. But, most garden ponds tend to have a higher ratio of fish to plants than an equivalent natural pond. In such circumstances, conditions in a pond will deteriorate unless an artificial means is used to prevent this from happening.

The two most important pieces of equipment in helping a garden pond to sustain life are a pump and a filter.

The function of a pond pump is to circulate water and therefore to aerate it to maintain a healthy balance in any garden pond or water feature. If you keep fish in your pond then aerating the water will provide them with sufficient oxygen.   

There are many different types of pond pumps available on the market of which they are fall into two main categories: either as a submersible or external (surface) models. It is therefore important to work out the water capacity of your pond before deciding on either a submersible or external pond pump.

For small and mediam-sized garden ponds, a submersible pond pump is a more economical and practical option. They can be placed directly into the pond and require little installation. Submersible garden pumps range in size or gallons per hour (GPH), from 50 to 50 000 GPH. For most garden ponds, pumps from 350 – 4000 GPH are perfectly suitable.

For larger ponds of 1000 gallons to 20 000 gallons (3 800 to 75 700 litre) or more, such as a Koi fish pond, it is usually a good idea to consider installing an external pump as they are more energy efficient.  External pumps are better for using with pressurized external filters as well. Other advantages to installing an external pump are that they are easy to clean, come with a removable leave trap which clog less often, generally last longer and are easier to repair and replace parts.

Although external pumps cost a little more up front, the energy savings will counter balance this initial outlay within the first year. It is, however worth comparing the running cost, as many cheaper pond pumps cost more in the long run once the cost of electricity is taken into account.

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