What is meant is aeration of the water or nutrient solution such as that seen in aquariums with airstnes that are connected via tubing to an air pump and that serves to push air into the solution producing gas bubbles that rise to the solution's surface. The point of this is to agitate the water and to create a current in the water that moves the lower water upward more rapidly than would be the case in a passive nonaerated solution that would depend on temperature gradients in order to produce a current of flow from the cooler lower levels to the warmer upper levels. What is generally accomplished by aeration is to induce a higher concentration of oxygen into the water while increasing the expulsion of carbon dioxide. Check out the link for access to a pdf treatment on this topic.

Here is a link that might be useful: Aeration in hydroponic gardening-a Chinese site

Hi, terrestrial-man,

Thank you.