must prepare the rockwool before you plant. Begin by saturating and conditioning it to lower the pH. Start by soaking the cubes or slabs overnight in nutrient solution with a pH of 4.5. To lower the pH of the nutrient solution, use dilute solutions of calcium nitrate, nitric acid, sulfuric acid, or phosphoric acid. After soaking, the pH of the nutrient solution should be around 5.5. When using new rockwool, the pH of the nutrient solution may rise for the first few weeks, so keep a close eye on it. If it rises above 7, saturate the rockwool in a dilute phosphoric acid solution with a pH of 4.0 for 30 minutes, then flush. This will help neutralize the alkalinity and stabilize the rockwool. For best results, run the system and make adjustments until the pH is stable before you start the garden. When it’s ready, drop a seed down into the premade holes provided in the cubes or slabs.