Rockwool
Rockwool media is a classic medium to use in mainly hydroponic systems, as is used as a starting point for your plants when they are too young to be put into a pure hydroponic system. Rockwool is an inert medium, and as such the plants do not need it directly to live. At a young age the plants can be planted in the system for the first few weeks of growth until their roots are developed enough to manage a bigger system. Rockwool is a great classic, as it is so easy to use, and cheap as well.
