Double Red Line Hard Akadama medium grain, imported from Japan. Used for Bonsai trees. Often combined with Hyuga, Canuma, Kiryu, sand, lava or composted bark. Akadama is one of the most popular materials used for soil mixes for bonsai trees. Akadama provides excellent drainage and aeration for healthy root growth as it porous allowing for absorption of water while spreading the nutrients inherent in its form to the bonsai trees roots.