The Circulation of water in your koi fish pond is very important. However, too much circulation (strong current) can stress and weaken your koi pond fish.
Too much water circulation in your koi pond causes your fish to constantly be swimming. It would be like placing you on a treadmill 24/7, you would become very weak in a short time.
One good indicator of too much circulation in your koi fish pond is, your koi fish will stay in one section of your pond in order to stay out of the strong current. Only leaving their “spot” to eat.