Prilled granulated stone wool is a soilless media that can be used alone or as an amendment to organic based mixes. Grodan Gro-Wool is designed to expand with water holding capacity that is able to hold 25-50% of its volume in water while aerating roots, maximizing growth. The water repellent granulates are superior substitutes for aerators such as perlite or Styrofoam. Grodan Gro-Wool is the only mix that the professional grower will need during the entire life cycle of the plant, leaving time for fertilizing, spraying and plant maintenance for efficient gardening.