Oase Pond pumps, The right pond or waterfall pump is extremely important to having a healthy, beautiful pond or water garden. The most important key to having clean pond water is to have constant movement and aeration. Stagnant water will allow unwanted algae to reproduce on the surface of the water. Not enough aeration can lead to low levels of oxygen in the water and that can be harmful to fish and other aquatic life. Also, if your pond pump or waterfall pump is too small or not strong enough, it may not be able to move enough water fast enough to keep it healthy.