Grow media describe the materials used to support hydroponic plants and their root systems - it's simply what the roots of the plants are growing in. Popular hydroponic grow media can include anything from saw dust or peat moss to old rubber tires. However, substances like rockwool, light expanded clay aggregates and coconut fiber are the most popular among hydro growers because of the support and moisture it provides, as well as the increased oxygen and aeration plants are exposed to.
The following are the most popular hydroponic growing media:
Rockwool - made from basalt rocks and chalk, is heated at 1600 degrees Fahrenheit (871 degrees celcius), to create lava. It's then blown into a spinning chamber, producing a texture similar to cotton candy. Rockwool fiber is then packed into mats and cut into cubes. The only downside to Rockwool is that it has some biohazardous disposal problems associated with it because it isn't organic.
Coconut Fiber - this organic medium maintains a larger oxygen and water holding capacity than rockwool .Coconut fiber is biodegradable, unlike rockwool, and it contains organic compounds, which many other hydroponics media lack.
L.E.C.A (or Light Expanded Clay Aggregate) - are also known as grow rocks, and are made by baking natural clay pellets at 1,200 degrees Celsius to create a porous growing medium - ideal for hydro growing. Although LECA is more expensive then other grow media, it can be reused in hydroponics growing.
Oasis Cubes - are referred to as starter cubes, and like rockwool, are small rooting cubes which come in long sheets. The material that makes up oasis cubes is similar to floral foam (used to design floral arrangements). Oasis cubes hold up to 40 times their weight in water, when saturated for hydroponic growing. However, they are not biodegradable.
Perlite & Vermiculite Combo - Perlite is a type of natural siliceous rock. When it's heated, above 1600 degrees Fahrenheit (871 degrees Celsius), Perlite pops like popcorn, creating thousands of tiny, light-weight bubbles. Vermiculite (or hydrated laminar magnesium-aluminum-ironsilicate) resembles golden flecks that can soak up to 3 to 4 times their volume in water. Vermiculite attracts calcium, magnesium, potassium and phosphorous - minerals that are vital to hydroponic plant growth. Both Perlite and vermiculite provide aeration and drainage. They can retain substantial amounts of water and release it to the roots as needed.