Yesterday I saw fish in the pond swimming clockwise in a circle, why?

Take out a fish and examine it carefully. Maybe it's a parasite that's eating away at the fish, and the fish are swimming all the way around for the sake of discomfort. Especially after a heavy rain, it is easy to wash the dirt outside the pond into the pond, and many land plants have parasites on the surface of the body. Pond fish pond wall must be high above the ground a height, to prevent the pond water pollution.