Rockwool is ideal for hydroponics. Not only is it safe for hydroponic use, but it also has many benefits for hydroponic production. Its structure is well adapted to retain moisture. This means that once it has been ideally saturated, it tends to stay put. This stability is important for any system where water flows. Plants grown in rockwool have a very important advantage that allows them to always extract water for their growth, even if the support displays a very low humidity. ... By allowing rockwool to drain freely, it becomes very difficult to overwater!