The function of the growing medium is to:

- provide support for the plant;
- ensure that water and nutrients are available to the plant's roots by absorbing and retaining moisture;
- provide air circulation and drainage around the roots; and
- to provide root protection against temperature changes. 

The media should not contain any of its own nutrients nor affect the pH of the hydroponic solution applied. Different media are suitable for different types of systems as well as being appropriate for different crops.

Growth Technology recommends two growing media – Cocopeat and Perlite.