The most widely-spread growing medium in hydroponics systems is, perhaps, rockwool. Originally used for insulation purposes and also known as mineral insulation, rockwool was first used as growing medium by Dane gardeners. Now, it is frequently used for drip-style indoor gardens around the globe.

Rockwool is produced by a process similar to making cotton candy: a particular mixture of sand and rock is melted and then turned into fibers by spinning the mixture to form products of multiple shapes and dimensions, from 1" starter cubes and up to large slabs of  3"x12"x36" in size. The variety of available forms and sizes turns rockwool into one of the most widely-used growing mediums.

How to Get Started with Rockwool

In order to start using rockwool as the growing medium for your hydroponic system, first of all, it is necessary to steep the material into water with a pH level of about 4.5 - 5.0. Just put rockwool cubes into a water-proof container and leave them for about 24 hours. When using a rockwool slab, first make a cut in the plastic wrapping of the slab, then pour in water with the adjusted pH balance until the slab is saturated, and leave the rockwool for 24 hours. Finally, do not forget to cut slits in the bottom of rockwool slab for drainage.

How to Use "loose" Rockwool

The major types of loose or granular rockwool are Hortiwool, repellant and absorbent. It is mostly used to fill containers for growing media with no limits in size. Another advantage of using such form of material is that it allows adjusting water retaining ability of the growing media in strict accordance with your particular need. However, working with loose rockwool, it is especially important to wear a mask for protecting lungs against small particles of rockwool whem using this growing medium for growing plants in hydroponics.