Oxygen need to be infused into the fish pond. An oxygenated pond produces healthy fish. A water-locked pond with poor oxygen lead to more fish death as other water creatures such as plankton consumes much of the oxygen.
Water aerator can be done in multiple ways. You can use air blower, paddle wheel or even water pump. The main purpose is to infuse the oxygen into the water, break the water surface for the oxygen on the water surface infused in the water. Aeration boost the oxygen level in the water. Directly or indirectly, it improves the water quality that make it more favourable for fish to live in.
Water circulation is also a way to combat mucky water that caused by decomposed materials on the water bed. It also circulate the warmer water with the colder water in the pond. This will reduce the chance of fish swim in the warm water and get killed.
Any kind of initiative you do as long as you can circulate the water flow in the pond provides a good pond water ecosystem.