Hydroponic/Fertigation Different Type Of Media & Its Characteristics

Media,One of the most obvious decisions a hydroponicist has to make is which medium they should use. Different media are appropriate for different growing techniques:

1. Diahydro - Natural sedimentary rock medium. Diahydro consists of the fossilized shells of algae (diatoms) that lived millions of years ago. Diahydro is extremely high in Silica (87-94%), an essential component for the growth of plants and strengthening of cell walls.
2. Expanded Clay - Also known as 'hydroton' or 'leca' (light expanded clay aggregate), trademarked names, these small, round baked spheres of clay are inert and are suitable for hydroponic systems in which all the nutrients are carefully controlled in the water. Clay pebbles are best not reused as even when they are cleaned. This does not remove roots that actually grow into clay beads. Breaking open a clay pebble after a crop has been grown in it will reveal this. Baked clay pebbles are porous,and can be irregularly shaped or uniform depending on brand and manufacturing process.
3. Rockwool - Rockwool is probably the most widely used medium in Hydroponics. Made from basalt rock it is heat-treated at high temperatures then spun back together like candy floss. It comes in lots of different forms including cubes, blocks, slabs and granulated or flock. When this medium is dry, care needs to be taken so as not to inhale any particles — inhaling such particles may carry a health risk. Rockwool will cause a higher pH level. You must adjust the pH level of the nutrient solution to counteract this. A pH level of 5.5-6.5 should suffice to create a suitable pH.
4. Coir or Coco-peat - from coconut husk fiber, can be used as a compressed medium. Coir comes also in bags and in slabs. Some types of coir are very high in sodium (salt) due to the nature of coconut palms growing on island environments and being processed in the salt air.
5. Perlite - 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.
6. Vermiculite - 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.
7. Sand - Sand is cheap and easily available. However, it is heavy, it does not always drain well, and it must be sterilized between use.
8. Gravel - The same type that's used in aquariums, though any small gravel can be used, provided it's washed first. It's inexpensive, easy to keep clean, drains well and won't become waterlogged. However, it's also heavy, and if your system doesn't provide continuous water, the roots may dry out.
9. Brick Shards - Broken up brick has been used in the place of gravel, works just like it, the disadvantage being that it may alter the pH and if recycled, has to be cleaned first.
10. Polystyrene Packing Peanuts - Very lightweight. Cheap, readily available and they drain well. They can be too light, and are mainly used in closed tube systems. Only polystyrene peanuts can be used: the biodegradable ones, of course, will become a sludge.

*Also refer to post Basic Needs For Fertigation 6 - Media Substrates