An Air Diffuser System is the best way to aerate ponds 10 Feet and deeper. The diffuser lies on the floor of the pond. You achieve complete pond aeration from top to bottom regardless of the pond depth. Although these units are not as effective as fountains for shallow ponds, you would have to place more diffusers in the ponds floor to properly aerate it.
Fountains are a popular choice when a more decorative aerator is desired. Decorative Lake Fountains splash the surface of the pond and help control surface algae and duckweed, but can't aerate down deep towards the bottom of the pond. The maximum depth you can aerate a pond with a fountain is about 6 ft deep. Decorative Fountains work best in ponds 6 ft or less.
A Diffused Aeration System is an effective method of aeration for ponds with 6' of depth or more. By using an air compressor that forces air thru tubing into the bottom of pond, a continuous flow of water moves upward allowing the upper and lower levels of the pond water to mix with little energy. In addition to adding vital oxygen to the pond, this allows the removal of waste gases and products.