Fountains are installed into ponds, and lakes for two reasons. One is aesthetic. There is a beauty to a water fountain. It creates an enjoyable environment where a person can relax and be refreshed. Lights can be added to make it even more beautiful. Beyond the aesthetic reason, there is another reason for installing fountains, and that is for the health of the body of water itself.
The water in lakes and ponds tends to naturally stratify or separate into layers. Each layer is distinguished by the temperature of that layer, as well as the amount of oxygen. During the summer months, oxygen tends to exist more towards the surface of the water, where the water meets the air. Warmer temperatures distinguish the surface waters. Cooler temperatures and less oxygen are found towards the bottom of the lake.
When the water and oxygen is not circulating freely in lakes and ponds, bodies of water become stagnant. The layers become more and more defined. Oxygen and warm water accumulate on the top layer. Cold water and a lack of water accumulate on the bottom layer. Then, all of a sudden, things can turn topsy-turvy. A summer storm can come with a downpour of cold rain. The rain descends to the bottom of the lake and stirs up the stagnant water that is oxygen-poor and sends it to the surface. This abrupt action by nature can cause fish kills.
There is another problem that can occur with stratification. When there is not enough oxygen at the lake bottom, animals and bacteria can use whatever dissolved oxygen is there. Meanwhile, in the process of the biological life of the lake, dead algae sink to the bottom of the lake. There, bacteria decompose the algae. This activity accelerates the depletion of oxygen in the bottom layer as the little bit that is left is used to help decompose organic material. When the oxygen is used, a different kind of bacteria that does not require oxygen begins to take over the task of decomposition. Nutrients become rich at the bottom of the lake as the decomposition is happening there. However, since there is no way to get those nutrients to the surface, algae living at the surface begin to die, adding to what is on the lake bottom. The anaerobic bacteria, those that do not require oxygen, continue to digest what is on the bottom of the lake. This produces hydrogen sulfide gas, which smells like rotten eggs
By having a fountain or aeration system, it helps keep an ongoing mixing of the surface and deeper water, and ongoing mixing of oxygen rich and oxygen poor water, and it leads to a healthier lake environment. A healthy lake environment means fewer toxic gases, less odor, life-giving oxygen for fish, a better environment in which food that fish eat thrive, and thus healthier fish. A fountain or aeration system, can provide these benefits of health to a lake, as well as aesthetic beauty.