The hydroponics growing medium of choice! Grodan Rockwool or stone wool is made from molten rock spun into cotton candy-like fibers and then compressed into cubes, blocks or slabs. Rockwool’s superb quality, fiber structure and pathogen-free content enables optimal root development for unrivaled growth and production.

Grodan has the highest density on the market, which translates into the greatest structural integrity for increased and longer oxygen holding capabilities. Low density rockwool collapses with the weight from water and plants, squeezing out air pockets and decreasing oxygen retention. High density gives better insulation value — especially important during germination and rooting of cuttings. Higher density also improves the wicking and dispersion of moisture and nutrients, enticing roots into more areas of the medium, and therefore increasing nutrient fueled sites for premium plant production.


Cubes (1.5″, unwrapped) are recommended for starts and cuttings. They fit into standard 1020 propagation trays, and may be transferred as needed to blocks or traditional growing mediums.

Mini Blocks (1.5″ & 2.0″, wrapped) are used for seed and cutting propagation. Each block is wrapped in white plastic on four sides and supplied in a convenient 23.5″ length of “tear away” strips.

Blocks (4″, wrapped w/40 mm hole) can support small to medium plants from start to finish. They are often used with cubes or slabs.

Hugo (6″, wrapped w/40 mm hole) provide enough growing volume to support a larger plant, so it does not need to be placed on top of a slab.

Slabs (6″ W x 36″ L x 3″ T, wrapped) are recommended for larger crops with extensive roots like peppers and tomatoes. Typically, seedlings in blocks are placed onto slabs.