Plants grow in specially designed channels such as gutters or PVC pipes. A watertight tank or tub periodically fills, then drains back into the nutrient reservoir. Drip gardens deliver a nutrient solution to plant roots using the same types of emitters as in outdoor drip-irrigation systems. Draining nutrient solution can be trapped and recycled, or allowed to drain away. Growing Media Instead of soil for root growth, hydroponically grown plants need a porous but stable and inert material.
Different materials can work, depending on the situation.
Washed, 20-grit sand, various gravels, redwood bark, polyurethane foam, coconut fiber, perlite, and vermiculite will serve. But the two you're most likely to encounter and use are rock wool and some type of expanded clay. Rock wool is manufactured by melting rock and extruding it into fine threads that are then pressed into loosely woven sheets. These sheets are cut into cubes, blocks, and slabs. Chief advantages are its ability to hold water and still provide excellent air circulation around roots.