All it takes is a simplet twist of a knob for this pressurised filter to clean itself automatically. This feature is activated by switching to the 'Clean' setting as this begis a process that squeezes the foams together which then forces out any pond sludge. When operating in the 'Run' position the water will be cleaned via a 4-stage purification process. This filter is powered by a 13w UVC and is capbable of providing clear water for ponds with a volume of up to 15,000 litres/3,000 gallons (in full shade and with waterplants).