The shape of the pond has an important bearing on efficient water circulation.
Good circulation to ensure good water quality.
Work out the best place to return biologically filtered water to the pond and ensure that it will create proper circulation.
Large ponds may require more than one return in order to achieve good circulation.
Water is normally pushed into the pond below the water line, except when it returns down a water course.
Implementing both methods means that the water course can be turned off in the colder months to prevent excessive cooling, while still maintaining flow through the filter system.
Sharp corners in the pond have a number of drawbacks.
When predators including humans approach the pond, the koi will be stressed and instinctively try to escape to the point furthest from the threat.
In doing so, the may collide with a wall of the pond.
If the corners are rounded off, a glancing blow may replace the risk of a head on bump.
Make sure there are no corners in which fish can be trapped.
In some parts of the world, the pond may need to be covered in winter, particularly if the water is heated.
The cover will reduce wind chill and minimize the drop in water temperature, so that less heat input is needed to maintain the required level.
Even if the pond is not heated, a cover will minimize water temperature swings and keep the water warmer than it would be otherwise.
It is a good idea to incorporate sockets or similar fixing points into the design of the pond surround for the convenience of securing a cover.
Keep any cover well clear of the water surface to prevent a jumping fish damaging itself.