Hydroponics gardening guide – growing mediums used in hydroponics – How to Use Rockwool Cubes and Slabs

How to Use Cubes

There are many different sizes of rockwool growing media cubes. The 1x1x1.5 inches and the 2x2x1.5 inches cubes are usually not wrapped into plastic and used as seeds propagation equipment. These are the so-called “starter cubes”. Another typical size of rockwool cubes is 1.5×1.5×1.5 inches. These cubes are usually wrapped with plastic on their four sides, which helps to slow down moisture evaporation. Such cubes are recommended for growing cuttings.

As the major growing medium either 3″ or 4″ cubes are used. They can also be used in combination with some other type of growing media. If the plants are small, such cubes may work well during the whole growing process. However, for growing larger plants such cubes may be too small and need to be replaced with or transplanted into the larger growing media as the plants get bigger.

By the way, some of the bigger cubes may have a special hole of 1 inch in size to make small cubes transplantation easier. Just insert a small 1” cube into the hole in the larger cube and transplantation is over.

How to Use Slabs

Though all the slabs have depth of 3 inches and length of 36 inches, their width may be either 6, 8, 10 or 12 inches. The most widely used sizes are 6″ and 8″, since they are big enough to suit practically any hydroponics system growing needs.

Rockwool slabs are supplied sealed into the plastic wrapping. Usually, slabs are used for transplantation of small cubes into them. In order to do that, one should make X-like cut in the top plastic cover of the slab (the size of the cut should match the size of the cube to be transplanted). After that, plastic tabs are lifted aside and the cube is placed on the slab. Some gardeners fix the cube to the slab with a toothpick or small plastic spike until the roots grow into the slab.