Enhance your soil. Use this expandable brick of all-natural coconut fiber to improve your soil, giving your plants the right place to stretch out their root systems. It will loosen hard clay soil and add water-retaining fibers to sandy soil. Resists compacting and remains porous for air circulation — the perfect, sterile growing medium. Grows to nearly 2 gallons when you add 1 1/5 gallons of lukewarm water.