Melih Oztalay our expert of the day, writes:

Hydroponics is crop production with mineral nutrient solutions instead of soil containing silt and clay. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel or rockwool. A variety of techniques exist.

Perlite is a volcanic rock that has been superheated into very lightweight expanded glass pebbles. It is used loose or in plastic sleeves immersed in the water. It is also used in potting soil mixes to decrease soil density. Perlite has similar properties and uses to vermiculite but generally holds more air and less water. If not contained, it can float if flood and drain feeding is used.

Like perlite, vermiculite is another mineral that has been superheated until it has expanded into light pebbles. Vermiculite holds more water than perlite and has a natural “wicking” property that can draw water and nutrients in a passive hydroponic system. If too much water and not enough air surrounds the plants roots, it’s possible to gradually lower the medium’s water-retention capability by mixing in increasing quantities of perlite.

Clint Jhonson our expert of the day, writes: