There are many other types of media used in hydroponic systems. Sand - Many sands, such as beach sand, have salts already in the media, that can cause problems in hydroponics. However, sand is a useful media that retains water. Sawdust - where there is an extensive timber production, sawdust may be available. The species of tree is important, with softwoods decaying more slowly than hardwoods.
Some sawdust is from logs soaked in salt water and is therefore toxic to plants.
Peat is very acid and can lower the pH of the nutrient water. Vermiculite - This is a volcanic mica which has been popped in a kiln. No media - There are many hydroponic systems that use no media whatsoever. The plant is usually started in a small piece of rockwool, or specially designed plastic collar. The plant is then placed in a growing tube or container that applies nutrient water to the roots.