The Different Hydroponic Grow Mediums
Rockwool is an inert, porous, sterile and non degradable medium that provides extremely firm root support. It is best suited for seedlings and cuttings.
You can get rockwool in slabs, cubes and granular flock. When rockwool is saturated it contains around 80 percent nutrient solution, 15 percent air space and 5 percent fibre.
Before you use your rockwool you need to make sure that you first soak it overnight in a low pH solution to lower its naturally high pH.
The best rockwool is very lightweight and you can get it with fibers running both horizontally and vertically. This apparant random structure promotes root growth in all directions.
Rockwool also comes wrapped in a thin sheet of plastic to guard against algae growth and to act as a container.
Coconut fiber, also called palm peat, cocos, coco peat and coir is probably the most popular hydroponic grow medium in the world.
Coconut fiber is actually the coconut pith that comes from just underneath the green husk that has been soaked in water and had all the salts removed as well as gums and natural resins.
Coconut fiber has many advantages over rockwool. It retains much more water and can hold onto oxygen better too. If you’re using an ebb and flow system then this really is better than rockwool. It comes with a pH balance of between 5.5 and 6.8 so unlike with rockwool you don’t have to pre-treat it before use.
Coconut fiber comes in compressed bricks, which when wet expands to about eight times their original size.
It also contains hormones which protects roots from fungus infestation. It really is easy to see why coconut fiber is so popular!
Expanded clay pellets are inert, lightweight, pH neutral and reusable. Clay pellets have air pores inside which means this is a hydroponic growing medium with excellent nutrient solution retention ability. Also, since they are round, lots of air is easily able to live between the pellets which stimulates nutrient uptake as well and also allows for fast drainage. You can increase drainage further by mixing the clay pellets with other hydroponic growing mediums such as coconut fiber.
Clay pellets are especially popular in hydroculture hydroponic systems. Also, if your growing plants that require extra good drainage such as roses then this should be the medium you use.
When you’re out shopping for expanded clay pellets, please keep in mind that it’s also called clay pebbles, expanded aggregate or expanded rock. You can also buy it in various sizes.
Soilless mix is great to use with wick systems. They hold lots of air and they retain water very well too. There are many different types of soilles mix and some even come with a variety of ingredients. You can of course even mix your soilless mix with other hydroponic growing mediums for good effect. Popular soilles mix includes:
Perlite – This is sand or volcanic glass which has been expande in heat. It holds water and nutrients very well. You can get perlite in three grades; fine, medium and coarse.
Vermiculite – This is mica which has been processed and expanded by heat. It holds water and nutrients very well. It also holds air great too within the fibers and gives body to fast draining soils. This is best used in wick systems and comes in the same three grades as above.
Peat moss – We all know what peat is, it’s partially decomposed vegetation mined from bogs. Peat is used to amend soil as a hydroponic growing medium. The first time you use peat, you’ll find it difficult to wet. You can get round this by mixing it with other components. Once you do get it wet it will retain up to 30 times its weight in moisture. This makes it great for hydroponic wick systems.