Rockwool cubes, or mineral wool cubes, are something like a sponge, but they are totally biologically and chemically inert. Rockwool cubes holds an enormous amount of nutrient solution and air at the root zone, two factors that indoor gardens like to have uninhibited access to. Rockwool cubes increase in weight many times when fully saturated but still provide the root zone with plenty of oxygen and opportunity for optimum nutrient uptake. Fully saturated rockwool cubes consist of not less than 18% air. A rockwool cube is made from molten rocks heated to 1600 °C and spun like cotton candy, making the growing medium sterile, strong, and slightly alkaline. Rockwool cubes seem like the perfect growing medium for an indoor garden - just add nutrients, water, and light and we're good to go, right? Maybe not...

The great part about a rockwool cubes sterility is that we can control exactly what organisms and compounds go into the root zones of our indoor gardens. Combine rockwool cubes advantages in holding air and nutrient solution with a traditional indoor garden grown in soil's advantage in meeting all of the other needs of a crop. Fungi, humic and fulvic acids, silicates, and other organic sources of nutrients such as bone and blood meals are all vital and necessary to a healthy and happy indoor garden.