What size heater do I need?
As a "rule of thumb" we recommend 1-kW per 1000-UK gallons of water, however this should be confirmed with your supplier as the ratio is very much dependant on the surface area of your pond / system. For example you could have a very large volume of water with a very small surface area (i.e. very deep) this would require less than 1-kW per 1000-UK gallons. On the other hand if you have a very large surface area and the same volume of water then the heater would need to be sized larger than 1-kW per 1000-UK gallons.