This filter and pump system is good enough for koi ponds containing up to 4,500 of water. The compact filter employs foam cartridges, brushes and Flocor media to ensure your dirty pond water is thoroughly filtered. It has a powerful 18w UVC unit built into the lid to keep your water clear of green water and is a doddle to clean thanks to the quick action back flush. A full de-sludge is also available by simple hose attachment (all filter media is held above the filter floor so valuable friendly bacteria will not be harmed by this process). The filter pump is economical to run and can handle 6mm solids. This set contains the following components (please click links below for more information): • Hozelock Aquaforce 4000 pond pump (note: skimmer not included when purchased in this set) • Lotus Clear Pond 18 box filter * Saving made when compared to buying items separately.