Hydroponic Growing Mediums
A good hydroponic growing medium is one that:
1. Should be able to stay pH neutral over change and buffer pH changes.
2. Hold nearly equal concentrations of air and water
3. Able to hydrate and re-hydrate quickly
4. Can be recycled/reused and is biodegradable
5. Cheap and easy to obtain
6. Lightweight and easy to move around both outdoors and indoors
The best hydroponic medium also depends on the type of hydroponic system you will use. The most commonly used mediums for hydroponics are: Coconut Coir, Agricultural Grade Perlite, Expanded Clay Pellets, Rockwool and Common Pea Gravel.
Other less common growing mediums include Composted bark, gravel, oasis, peat moss, pumice, sand, saw dust, soiless mix(s), Vermiculite and gravel.
You can mix mediums together. For example Coco Coir is often mixed with 50/50 perlite to provide a higher air holding ratio than Coconut Coir alone. Also a good combination is
My Favorite growing medium is coconut coir otherwise known as coconut fiber. Coconut coir combines the air retention of perlite, with the water retention of vermiculite and it is a completely organic medium. It can be reused and is biodegradable, relatively cheap and easy to obtain. It is also lightweight and easy to work with. Another benefit of using Coconut coir as a growing medium it offers plants protection against fungus and root diseases due to its anti-fungal properties. For all of these reasons coconut coir is becoming one of the most popular growing mediums amongst hydroponic gardeners.
The advantage of Perlite is that it has excellent oxygen retention and is very lightweight making it easy to transport. It mixes well with other growing mediums. For example it can be mixed with soil and soil free mixes to provide greater oxygenation for the plant roots.
While its lightweight properties make it easy to transport and work with a disadvantage is that it can get washed away in some hydroponic systems, for example the Ebb and Flow system. However it works well with the wick type hydroponic systems as perlite has good wicking action.
LECA stands for Lightweight Expanded Clay Aggregate and is very loose with large grains. The advantage of expanded clay pellets is that they remain pH neutral and are reusable. This makes them cheaper and environmentally friendly. The advantage of clay pellets is the shape and internal structure of the pebbles which ensures good root aeration and drainage and helps prevent rotting.
The disadvantage is that expanded clay pellets are dusty, so they will need to be rinsed thoroughly before going into your hydroponic system.
Rockwool is made from molten rock that has been spun into long, glass-like fibers. Rockwell is usually sold as cubs or in a loose form. Rockwool is used in wall insulation and is popular amongst the commercial greenhouse industry. The advantage of Rockwool is that it can be used for a wide variety of hydroponic systems, it easily absorbs water and drains well. It’s also completely sterile and non-toxic and makes for a good starting medium for seeds, cuttings and small immature plants. If your system constantly recirculates your nutrient solution, a fast draining medium such as Rockwool is ideal.
The disadvantage of Rockwool is that because it is not natural, it is not biodegradable. Gardeners have complained of the substance irritating their skin.
Pea gravel is made up of stones less than an inch in size. Like expanded Clay pellets they remain pH neutral and are reusable. Unlike expanded clay pellets they are heavier which can make transportation more difficult.
The advantage of using a heavy grow medium is that the medium does not get washed away with Ebb and Flow type systems.