The proper pump can save you money by consuming less energy, and save you time spent on maintenance. The two most important factors to consider when choosing a pond pump are:
Gallons Per Hour (gph). It is important to know the volume of water in your pond to be sure that sufficient circulation occurs. You also need to make sure the pump is adequate to run your filtration, waterfall or any other added components. As a general rule, circulate pond water a minimum of once every hour. Insufficient circulation can cause areas of stagnant water, low oxygen levels, and many other problems, which eventually lead to an unhealthy pond.
Max Head Height is the maximum height that a pump is capable of pushing water. This is useful if you will use the pump to move water to a waterfall or through a filtration system. So, before purchasing a pump, you need to consider elements of your pond design that affect head height.