The Natural “Coir” Block contains only coconut pith and fibers. Great for water holding capacity these materials also provide plenty of aeration and drainage. These high quality, low sodium, growing media are an environmentally friendly alternative to sphagnum peat moss. When hydrated with water, Cocotek Bricks and Blocks rapidly expand, which saves you time and effort. GH Cocotek growing media can be used exclusively by themselves, blended together or mixed with expanded clay pebbles, perlite or topsoil.