Aeroponics is basically hydroponics with a twist. Instead of using a growing medium to anchor roots and run a solution through, the roots are suspended in air and are fed with periodic mistings that are set with a timer. In contrast to top-feeding systems, misters are connected to the ends of the 1/4-inch tubing and a stronger pump is used.
A simple aeroponic system can be built by placing 2-inch thick styrofoam on top of a solid, leakproof table. It is best to have the root environment well draining so that roots don’t sit in a few inches of slow-moving water.
Another alternative is using PVC pipe or gutter pipe to hold plants in place and to allow the solution to drain back into the reservoir.
One more method is to use a small mesh pot inserted into a larger pail (ie. 5 to 7 gallons).
Aeroponics is cutting-edge horticulture and can take a grower far if he has sound knowledge of hydroponics. Aeroponics can also be of assistance to novice growers for the fact that there is less medium (e.g. clay) to hold salts that hinder growth. However, there are hydroponic methods that use mediums that do not contain too many salts, such as perlite.
A disadvantage of an aeroponic system is the higher cost of the high-powered pump that is necessary to create a highly aerated mist. Another disadvantage is the possibility of large gardens having clogged misters. When misters get clogged during hot hours, there is only so much time to fix the problem before the wilting damage is irreparable.
Many top-feeding hydroponic systems can be converted to aeroponic systems by using a stronger pump, adding a mister for each plant, and changing the position of the mister to feed roots in the air as opposed to top-feeding.
Hydroponic systems that use less growing medium will work best, such as those grown in PVC or gutter pipe. Otherwise, flood and drain tables can be converted to aeroponics by putting on a cover such as styrofoam. Hydroponic systems that use very little medium make for an easier conversion.
The links below will take you to DIY aeroponic systems.