The huge collection of Lotus Green Genie Pond Filters are designed to offer top quality filtration in your garden pond. A Koi pond especially needs sufficient filtration to ensure clean, clear, healthy water.Each unit has an integral Philips Ultra Violet lamp which treats algae cells in the water. They are clumped together for easier removal. Removing the algae from the water lowers the risk of an algae problem in the summer months. The larger models from 12,500 upwards come complete with two lamps to ensure that larger bodies of water are properly treated.The water then flows through Dimple foam of different grades, so particles of every size and shape are removed from the water. Flocor biological media then uses bacteria to break down nitrites and other biological pollutants which improves water quality and cuts the risk of health problems in fish and plants.All of the filters are fitted with a Vari-Flow valve which guards against over-flowing.