Aeration to Control Phosphorus Levels Within Ponds
On reason that "internal fertilization" is such a problem is the tendency of even shallow ponds to become anoxic near the bottom during the growing season. The lack of oxygen allows phosphorus to remain in a dissolved state, and thus subject to easier return to the water column. Aeration, in addition to providing oxygen needed for the survival of fish and other animals, is thus a useful way to keep internal fertilization at a minimum.
Aerators work by pumping air to a point near the bottom of the pond. Pond water mixes with the air bubbles as they rise to the surface, and absorbs oxygen both during ascent and at the surface. Commercially-available aerators may be powered by electrical, solar or wind energy, and come in a variety of designs suitable for a wide range of pond sizes. A number of firms in southeast Pennsylvania market and install aerators, and can be found on the internet.
Some aerators (termed "bubblers") are rather inconspicuous, evident largely by the roiling of water at the surface. Fountains are also frequently seen in ponds of this region. Fountains often provide some degree of aeration, but in many cases draw already well oxygenated water from just below the surface. The function of many fountain systems thus is largely one of decoration rather than of pond management.