Rockwool (Stone wool) is an excellent substrate used to grow plants hydroponically; an extruded wool-like product formed through a process of melting rock and extruding it into threads like cotton candy and pressing it into loosely woven sheets at high temperatures. Stonewool products are also available in grow blocks and slabs in various sizes. Grodan also makes ParGro, a stone wool media with excellent drainage properties.

What is Stone wool?

stone wool fibers compressed between fingersplant growing in rockwool block

Stone wool or Mineral wool is created from rocks, the raw materials are basalt rocks and chalk, which are then melted down and spun into fibers using air. These fibers are packed together into a mat and then cut into various desired configurations for various uses from hydroponics (as a growing medium) to soundproofing, filtration, and even thermal insulation. The main reason for using stone wool in a hydroponic growing system is to provide a buffering reservoir of nutrient solution in the root zone while maintaining an adequate volume of air (oxygen) in contact with the roots, thus promoting healthy root growth.

Grodan Rockwool

Grodan Rockwool products

Rockwool is a stone wool soil-less media product made by Grodan for use in hydroponics. Stone wool is the main reason that most of the world’s greenhouse vegetables are now grown hydroponically. Rockwool slabs and cubes come in various sizes and shapes and sizes from slabs to grow blocks and plugs. Rockwool, at full saturation, holds approx 80% of its volume in water, leaving 20% of tiny air pockets that help to stimulate root growth. Best suited for hydroponic systems like flood & drain and top feed, drip systems.


various ParGro products

ParGro Quick Drain (QD) is a version of stone wool media with better drainage properties than the original GRODAN Rockwool and comes in various sized slabs and plugs for use in applications such as ebb & flow systems.