Adding a small fountain to your pond not only adds some dynamic sights and sounds to your pond with water spraying into the air and splashing back to the surface, but it also increases the aeration and circulation in the pond.
A small recirculating fountain can also be used as a winter de-icer by taking the pump from the bottom of your pond, putting it on a shelf, and adjusting the outlet to stir up the water right below the surface. This will keep a hole in the ice in the winter and also provide for your fish the much needed circulation and aeration.