hydroponics, a soilless grow medium is used to help plant roots support the weight of a growing
plant. Many different types of media can be used in a media-based hydroponics system, including rockwool, coco coir, expanded clay, perlite, gravel, vermiculite, growstones, and more. Ultimately, the choice is made based on personal preference, budgets, availability, system design, and irrigation methods.
Media-based hydroponic systems can include nutrient film technique, ebb and flow, top-feed systems, and drip systems. In each of these systems, the grow media is housed in either grow trays, grow containers, grow beds, or troughs. It is also the area of the system which is irrigated with nutrient solution.
To be suitable for use as a grow medium, it must be inert and resistant to mold growth. It must also not be so lightweight that it floats. In most forms of hydroponics, media must be used to support growing plants. Grow media gives roots something to grasp and grow around while supporting the weight of maturing plants. In many ways, it replaces the soil in which a plant would naturally grow. However, this media is inert, meaning that it provides no nutrients or beneficial microbes at all – only support.
Many different types of media can be used in this method of hydroponics. Rockwool is one of the most popular, as is expanded clay aggregate, coco coir, and perlite. Sand, saw dust, lava rocks, and even plain gravel have all been used with varying degrees of success in media-based hydroponics.
Different types of media work in different ways and offer unique benefits. For instance, gravel will last for multiple decades, but may need more frequent cleaning than other materials to remove mold. Coconut fiber is 100% natural, but will eventually degrade and decay. Other types of mediums can offer a permanent solution, but may cost more to implement.
Removing the growing media from hydroponics changes the set-up completely. For example, most deep water culture systems see plants supported by rafts, and roots dangling freely in a nutrient solution.
When roots are bare and dangling in air, it becomes aeroponics rather than hydroponics. In this system, the roots are free to float in air, while the nutrient mixture that delivers vitamins, minerals, and water to the plants is dripped down from a drip line above each plant, or else misted onto the roots directly (i.e. fogponics).