Substrates for hydroponics and aquaponics

A substrate, also called a medium or media, is a supporting material or base on which a plant can grow. The most commonly used substrates are: Rockwool, lightweight expanded clay aggregate, coco coir, coco chips, perlite, vermiculite, peat moss, lava rock, river rock, and sand. Some uncommonly used substrates include: oasis cubes, floral foam, growstones, pine shavings, pine bark, polyurethane foam, water-absorbing polymers and rice hulls. A good substrate supports the plant, allows for air flow, and is porous.

Buffering capacity is a measure of how efficient a substrate resists changes in pH. A high buffering capacity will neutralize a nutrient solution if an acid or base is added. Porosity is the amount of open space that allows for air exchange in a substance. A high porosity material will allow for more air exchange. Water holding capacity is the amount of water a substance can retain. A substrate with a low water holding capacity does not retain water well. Cation-exchange capacity is the amount of salts or ions a particular substance can store. A high cation-exchange capacity would allow for a high salt content in the material that may be used at a later time when the liquid solution may be devoid of salt content.

Read more at the Stuppy blog (Scott Moore)