Location - as per a traditional pool, but consider a location nearer to the house, both for viewing and security. If plants are avoided, a location in part shade is more applicable, or consider building a pergola or similar. The pools potential depth and filtration requirements may mean careful consideration of services (i.e. drainage pipes and mains).
Size - if koi (and orfe) are a long term addition, the their potential size calls for a larger pool, especially if you wish to build up numbers. Depending on filtration, provide approximatley 250-900 litres (55-200 gallons) per full grown koi. It is also preferable to avoid building a pool with a surface area of less than 4 sq. metres (43 sq. feet) and a volume less than 2300 litres (500 gallons).
Design - there is a general preference towards semi-formal or formal, and raised or partially raised pools. The fish's origins and the sparse planting suit an oriental style. A simple shape is preferable to allow for easier construction, as well as maximising the volume and surface area in any given space.
Filtration - where there is a total absence of, or light planting, especially combined with good fish stocks, then biological purification of the water with a filter is essential, as is an ultra violet clarifier to control green water.
Fish - this type of pond is designed with the fish very much in mind but make sure that your filtration matches your fish stocks especially in the long term.
Recommended lining materials - a flexible liner is ideal if sheer sides are not part of the plan. Otherwise, concrete blocks finished with a butyl liner, fibre glass or a treated render is best bet.
