Hi Stef
You have three options:
1 High pressure pool pump (0.45 kilo watts) Example: Porpoise Speck Pool pump
Cheapest pool pump put consumes more electricity per water delivery. Suitable for a two bag sand filter.
Up to 15 000 liters
Costs: R 1100 to buy
Monthly costs: 0.45 kilowatts per hour @ approximately 30c per kilowatt hour = 0.45 x 30c x 24 hours x 30 days = R 97.20 per month depending on the costs of electricity in your area.
2 Lower pressure higher flow rate pump (0.45 kilo watts)
More expensive but on the long run, cheaper because of lower electricity consumption. Also .45 Kilo watts but provides a higher flow rate.
Costs (R 2000.00)
Monthly running costs: almost the same as above but higher flow rate.
3 Submersible pump ( 165 watts = 0.165 Kilo watts - 8000 liters per hour)
Costs: R 550
Running costs: 0.165 Kilo Watt / hour x 30c x 24 hours x 30 days = R 35.64 per month
Lower flow rate, in this example 8000 liters per hour.
Disadvantage: Low pressure (maximum hight 3 meters) and can not be used with a sand filter, but very economical and cheap.
If the water does not have to be raised, this pump is suitable for a 10 000 liter pond(will turn the water around at least every two hours) However, if you have to raise your water to a waterfall, your flow rate falls dramatically. At 3 meters the flow rate is only about 1000 liters per hour as apposed to the 8000 liters if the input and output is on the same level.