In the coming articles, we’re going to investigate some of the top choices for your hydroponic growing medium. We will look at the advantages and disadvantages of each, and how to properly prepare and use them to maximize your results. Whether you’re on the fence about going hydro or a veteran, stick around as there is something for all to learn!

Rock What?
What do you get when you melt sand and rock down and then spin it into a fibrous material, much like a favorite fair food? A tummy ache? No. A highly efficient support system for your plants? Yes! Stonewool (or more commonly called rockwool) keeps plants immersed in a perfect ratio of both water and air due the pockets of air between the fibers and the capillary action of those fibers. Rockwool comes in many shapes and sizes, which allow it to be used for different stages of plant growth. Starter cubes are used for propagation, and big blocks or slabs are for larger plants that need more support. Often rockwool is the starting medium before being placed into net cups filled with hydroton. Rockwool slabs and blocks are most commonly used with drip irrigation but can also be used in other hydroponic systems. Rockwool also comes in granulate and chunk form for filling up containers.

Prepare to…Rock!
Rockwool is naturally inert and pH neutral. However, in the manufacturing process limestone residue cakes the fibers which causes it to become alkaline, and therefore treatment of rockwool before planting is very important. To prepare rockwool it will need to be soaked for 30 minutes to one hour in water pH adjusted to 5.5. A step many users forget is the need to flush the rockwool with fresh 5.5 pH adjusted water after the initial soak. This is one of the most important steps! By flushing afterwards you are completely removing the lime which would otherwise get into your system and have you racing to keep your pH in check. After treatment it is not advised to squeeze the medium as you can damage the structure and thus alter the air to water ratio and essentially lower the mediums effectiveness.
  
Feel the Fibes
Rockwool’s fibers provide a perfect environment for roots to grow and expand, allowing the plant to support itself. The spaces between the rockwool fibers encourage root hair growth which directly influences the plant’s ability to uptake nutrients as well as its growth rate. Rockwool fibers are generally woven in two directions - horizontally or vertically. Vertical arrangement, as found in the Grodan Expert slabs, promotes quick root penetration and encourages prolific vegetative growth. Horizontal arrangement like the Grodan Classic slabs will result in a drier media. Your choice of rockwool arrangement will depend on your specific goals, method, and system.