Koi pond  Koi ponds are ponds used for holding koi, usually as part of a landscape. Koi ponds can be designed specifically to promote health and growth of the Nishikigoi or Japanese Ornamental Carp. The architecture of the koi pond can have a great effect on the health and well being of the koi. The practice of keeping koi often revolves around "finishing" a koi at the right time. The concept of finishing means that the fish has reached its highest potential. Koi clubs hold shows where koi keepers bring their fish for judging. The skimmer allows water to be drawn from the surface of the pond. It collects leaves, pollen, twigs, uneaten food and all other kinds of floating debris. The skimmer usually has a clean out basket that can be quickly emptied on a regular basis to allow the skimmer to run properly. Most floating skimmers will also have a foam that sits underneath the basket to filter out the finer particles. Bottom drains are not required in water gardens but are very beneficial for Koi Ponds. When used in a pond that does not have rocks on the bottom, a bottom drain allows the heavy solids to be carried to the mechanical filter. In addition, many bottom drains are equipped with air diffusers, adding much needed oxygen to a pond. Mechanical filtration can be accomplished in many different ways. The job of this filter is to trap solids, preventing them from clogging the Biological filter. The mechanical filter should be backwashed or cleaned out often. Types of mechanical filters include Vortex, brushes, matting, sand and gravel, sieve screen, and settlement chamber. Biological filters convert the nitrogenous wastes from the fish. This cycle is called the nitrogen cycle. A biofilter can be constructed in many different ways. It is important for the koi keeper to understand how the filter is to be cleaned before they install one. Proper and regular cleaning of the mechanical and biological filters is critical for the health and quality of the koi. Bio-filters are sometimes divided into sub groups such as aerated or non-aerated. Types of bio-filters include:   An ultraviolet light is used to make algae flocculate (form into clumps), so that they can be removed by mechanical filtration. The UV sterilizer will also kill free-floating bacteria in the pond water. Water pumps move water through the filter system and back to the pond in a recirculating manner.