Garden pond pump choice.  What to consider...

1. To keep electrical consumption as low as possible, choose the pump that gives the correct performance without the need to throttle it back. Relying on a tap controller to restrict the flow on a large pump wastes electricity so choose a pump to give the appropriate, unrestricted flow.

2. Decide upon the appearance and actions you want the pump to provide. Is the pump required to pump water to a fountain or waterfall, or to circulate water around a pond or watercourse, or is it to pump water through a biological filter, or all of these combined? It's recommended that you circulate all the water in your pond once every 2 hours.

3. In some ponds, it's better to separate the pump actions and use 2 pumps. Use 1 pump to run 24/7 through a biological filter to keep the water clear and healthy and use the second pump as required to run the fountain, waterfall, wet wall, or sheer descent feature.

Information you'll need...

a.  Pond volume (length x width x depth).
b.  Head height for lift where you need to pump water up to a waterfall. This measurement is the vertical height between the surface of the water (pump reservoir) to the horizontal plane level to the outlet of the pipe. The higher the head, the higher the pressure required. Pumps with lower head capability use less energy.
c.  Tubing length required to take water from the pump up to a waterfall or pond filter system or to direct water to some other area of the pond. The larger diameter the better. Larger is better as it allows for less resistance.
d.  Determine watercourse dimensions. A pump for a watercourse or stream requires a high performance pump depending on how much water you want flowing. A watercourse of 100mm of flat water requires 1000litres / hour.