Pond heaters can help stop a pond from freezing over during the cooler winter months. Another use is to raise water temperature in order to maintain feeding or complete a pond treatment etc.
Cloverleaf Pond Heater Info
This heater from Cloverleaf is designed to be connected on the pump out flow and requires a minimum flow in order to operate of 4000 litres per hour..
Full instructions for installation and use and supplied.