Water movement – Water movement in a pond is important for 3 reasons. The 1st reason is that the koi need the exercise, especially if you are trying to grow large koi. Without lots of exercise the koi loose their appetite. Additionally, their ability to digest the food is decreased. This can cause the koi to develop a very large “pot bellied” conformation. The 2nd reason water movement is important is for better water quality. Without good water movement dead areas can develop in the pond where the water barely moves. These areas can become cloudy with algae and decomposing matter and prevent the pond from ever really looking clear. Finally, the 3rd reason why water movement is important is because good water movement can add oxygen to the pond.
One of the best ways to create good water movement in a pond, besides a good waterfall, is to add jets to the pond. I would never build a pond without jets in it. See design plans for more details on jets and their placement.