Having decided on the shape and style of the pond, you must consider its physical dimensions.
These will determine the volume of water it will hold.
A vital dimension is the depth of the pond.
A koi pond would not normally be less than 1.
35m (4ft 6in) deep.
Most koi are bought when they are small, but can grow to a considerable size.
If you do not take this factor into account, it will invariably mean that you will need a larger pond in a few years time.
However, if a pond is built to accommodate future growth, then those small koi will look totally out of place in it.
Buying some larger koi at the same time will help to fill out the pond in the meantime.
If you intend to keep large koi in your pond, particularly if they are to be of show quality, you will need a large pond.
A reasonable depth and a long swimming area will exercise a fish's swim bladder and muscles, as well as maintain body shape.
A pond that would allow for potential growth of the koi within it would probably be at least 20 cubic meters and subject to a limited stocking rate.
However, you should also consider the problems posed by a large pond.
Maintenance tasks are more difficult when carries out at arm's length and it is easier to net a fish when not trying to maneuver a long net in very deep water.
If a pond is 2.
5m or 8ft wide and the water is 2m or 6ft deep, the average person will require a minimum handle length of about 3m or 10ft.
Larger fish will need a large diameter net on the end of the handle.
If your koi are longer than about 45cm or 18in, you will almost certainly need a 75cm diameter net to reduce the possibility of damaging the fish.
Such a net can be very difficult to maneuver in the pond.
If the pond is wider or deeper or both, you will need a very much longer handle and a second person with another net to help you.