It is vital to maintain a very high level of oxygen in a garden pond. The oxygen content in the pond is subject to heavy fluctuations. This is because plants and algae which produce oxygen during the day through solar energy, switch their metabolism at night and use up most of the available oxygen. This natural process depletes almost all of the oxygen supply. Therefore, the survival of the fish and other organisms is especially endangered during the early hours of the day. The oxygen depletion problem is magnified through dead algae, plants, or superfluous fish food, particularly in warm water. These microorganisms use up an enormous amount of oxygen. This reduces the oxygen level for the fish and other organisms, thereby threatening their survival. In other words, when the biological balance is destroyed, pond life could die within a few hours.