Water aeration is one of the vital conditions of normal existence of living creatures in the tank, especially if there are many of them. Forced aeration favors gas regimen in the aquarium and promotes saturation of water with necessary amount of oxygen. The more active is the diffusion of air that comes in numerous tiny bubbles, the larger is the contact surface of water with the air and the process of water oxygenation.
Fish breathe oxygen and exhale carbon dioxide, which is consumed by the water plants during photosynthesis. Aquatic plants, in their turn, release oxygen. If the number of fish and amount of plants in the tank are well balanced, they excellently grow and develop together. If the number of fish exceeds, they undergo oxygen shortage, attempt to jump out water and hang close to the surface, gulping the air.
In the described case forced aeration can help. It is carried out by means of an air pump. The atmospheric air is collected by the device, comes along the tube through the airstone into the water. The airstone diffuses the air flow into minute bubbles.
Gas exchange, i.e. oxygen enrichment and removing of carbon dioxide, takes place mainly at the water surface. The flow of bubbles from the air pump drags the lower water layers (poor of oxygen) right there. Gas exchange occurs at the surface of each bubble too. The smaller are the bubbles, the bigger is their total surface and the better is the oxygenation of water.
The circulation of water layers also helps to level the vertical gradient of temperature in water: the upper layers are colder and the lower are warmer. Due to forced aeration the water temperature becomes even throughout the volume. Beside this, aeration destroys the fat pellicle that often forms at the surface of the steal water and prevents passive aeration.
At night the aeration by means of air pump is especially important, since the photosynthesis goes only in the presence of light. In the darkness the abundant plants may consume a bigger amount of oxygen than they have released during the daylight.
Air pumps and air wheels can be used as they are or be connected to filtering devices to increase the water flow through the filter.
Aeration should be conducted 24 hrs a day. Thus the stable gas regimen will be provided. Periodic, short-term, so to speak, boost pumping may rather do harm to fish and water plants, because it provokes jerky leaps of oxygen amount and hampers their vital functions.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).