Rockwool is an inorganic and sterile growing medium made from spun molten rock. A superior medium for rooting cuttings, rockwool provides 20% air space when saturated, and does not contain nutrients. It is recommended that rockwool be conditioned by soaking for eight hours in a pH 5.0-5.5 and then rinsing with pH 7.0 water. Water daily. Rockwool Cubes are great for rooting cuttings or germinating seeds. We recommend soaking them in pH 5.5 water overnight, and add seeds or cuttings the next day. Keep them under a dome to retain moisture and mist if necessary. From here, you can transplant into any growing medium, soil or hydro.