Rockwool, or mineral wool, has become a primary medium for propagating seeds and mothering seedlings in hydroponic gardens. Made from natural stone and chalk, it was used originally in building construction as insulation against sound and heat because of its porous structure. That form lets mineral wool do two things, reducing stress for gardeners, especially beginners:

• It keeps water and nutrient levels just right.
• It helps to promote strong young roots by allowing oxygen to reach them.

Mineral wool is manufactured in forms convenient for gardening, and it's easily cut into any shape or size needed.

Grodan Stonewool

Hydroponics gardening began years ago with stone-based, highly porous Stone Wool as a medium for growing when soil was unsuitable. It’s so effective that it’s still widely used in greenhouses worldwide to grow vegetables hydroponically. Here’s why it works: Stone Wool can hold 80% of its volume in water or nutrient solution, with oxygenated air filling the other 20% of its cavities, making roots strong. Although its pores hold water, the stands themselves do not soak it up. Buy Stone Wool plugs, blocks, or cubes, or buy slabs that are cut easily with shears, a saw, or even a bread knife. Stonewool is best suited for hydroponic systems like flood and drain top feed, and drip systems.

ParGro

ParGro Quick Drain (QD) is Stone Wool made by Grodan to drain better than original Grodan Stone Wool. Choose from slabs and plugs in a range of sizes for use in ebb and flow systems.