Hydroponic Growing Medium

The growing medium for hydroponic cultivation should be inert and should not affect the chemical composition of the nutrient solution. A good hydroponic medium should hold an equal ratio of water and oxygen. Sand and gravel do not make good growing media although course gravel can be used as long as the system constantly circulates nutrient. Some common and readily available hydroponic mediums include:

Coconut Fiber:

A new concept gaining popularity. It holds the perfect amount of water and air. Coconut fiber is a renewable resource which would otherwise go to waste as a food byproduct. It contains natural hormones needed for germination and cut-rooting and is naturally resistant to fungus and biodegradable.


LECA:

An acronym for Lightweight Expanded Clay Aggregate; LECA is made with expanded clay which is porous and and holds the perfect amount of water and air. LECA is pH neutral and will not alter your nutrient solution in any way. It is reusable and easily sanitized. Always rinse new LECA before use to remove any dust particles.


Rockwool:

Commonly used and the most widely available hydroponic medium. The main advantages are that it is reusable and can be completely sterilized. Rockwool can be used for starting seeds and rooting cuttings which are easily transplanted. A dust mask should always be used when handling rockwool.


Pea Gravel:

Can be used but is not recommended. It is only suitable for systems that constantly circulate nutrient like the waterfarm. It is heavy and non porous.

There are many of options when choosing a growing medium, and new ones are always being introduced. An important thing to remember when choosing your medium is to use proven ones. Using an untested or unreliable medium can change your nutrient pH, introducing harmful chemicals which will then be absorbed into the plant and eventually into your body if consumed. Some loose mediums can clog pumps and spray heads, reducing flow and decreasing the life of your pump.


All media needs to be rinsed and sanitized before use. Rinsing new media before use is necessary to remove any small particles. Sanitizing media can be difficult but it is necessary because using unsanitary media can introduce fungus and bacteria to your system that can easily propagate. Steam is the safest method for sanitation. Using a pressure cooker is a good option for the home gardener and will completely sterilize the media, killing all fungus and bacteria. Heating the medium in your oven is another way to pasteurize your media. Soaking the media in a mixture of 1 teaspoon of household bleach per gallon of cool water for 30 minutes can also effectively sanitize your media. Make sure to flush well with hot water.