Perfect for small koi ponds up to 10,000 itres gallons or goldfish ponds up to 20,000 litres 2,200 gallons.this eazypod comes complete with a built in uvc and air pump set all you need to do is to add a pond pump! Dirty water enters the filter and heavy solids are forced down and out out by the vortex created by the cylindrical water flow.finer particles get caught in the static kaldnes biomedia. Clean water then returns to pond to clean the filter simply turn the direction of air flow from your pond to the filter the biomedia 'bubble up' releasing the dirt and this dirty water exits to waste. Once the water looks clean simply redirect the flow of water and air back to your pond. Simple and no need to get your hands dirty! No wonder this product has made such an impact on the pondkeeping market, it's simply brilliant. Br br note uvc bulb included.