Why do you need a pond pump - what benefits does it bring to a garden pond?
A pond consists of a trapped body of water - perhaps created naturally by a dip in the lie of the land - or man-made by using pond liners as a water retention device.
The function of pond pumps are to move and circulate the water in the pond. This movement agitates the pond to avoid it becoming settled and stagnant - it also helps to introduce additional oxygen into the water. Oxygen in the water is vital to sustain life such as plants or fish. Once an oxygen-rich pond has been created it is important to keep the pumping process going if the pond contains wildlife as otherwise the sudden depletion of oxygen can kill pond fish and other pond dwelling creatures. It is correct that pond plants can create oxygen for a pond but this process is reversed during the night when they take oxygen away from the pond. Also the amount of oxygen created by such pond plants -sometimes referred to as pond oxygenators - is generally quite low compared to the additional oxygen created by splashing and moving the water via a pump.
If you want to master your pond's eco-balance then a pond pump is a vital piece of pond equipment. As well as the health benefits this movement of water also offers up other opportunities. For instance the water can be pushed through to a pond filter that can sieve out dirt particles from the pumped water. (note: This process works best with larger 'solids handling' pond pumps - these pumps sometimes referred to as filter pumps can pump solid pieces of matter up to the pond filter where the dirt is caught in the pond filter media).
Alternatively the pumped water can create a fountain - where the pumped water is pushed up through a fountainhead and into the air creating a pleasing display. Using a fountain pump a substantial amount of additional oxygen is added to the pond as the propelled water falls back down and breaks the pond surface. Another way to create an attractive natural looking feature is to create a waterfall - the cascading water hits the pond surface and generates a good supply of bubbles and oxygen.
It is important to remember that some of the features discussed in this piece can be combined. For instance, quite often a filter pump will be used to push water up to a filter and the water will return via a waterfall after it has been filtered. Similarly, larger fountain pumps will ship with a T-piece allowing the flow to be adjusted between a fountain and waterfall or ornamental spitter.