We prefer to use rockwool grow cubes, but many people prefer to use large, continuous slabs of rockwool. Rockwool slabs can be used in a variety of techniques, including instances where the nutrient solution is heated. Slabs are used where one continuous medium is required, whereas cubes are placed into another medium, such as clay pebbles. So, rockwool slabs would not be used in conjunction with the HydroPod hydroponic system, which uses clay pebbles.

Rockwool is a porous medium containing hydrophillic [water loving] fibres and hydrophobic [water avoiding] fibres. This is intended to prevent the medium becoming saturated with nutrient solution, although this is still possible. Water-logged grow media prevents air reaching the roots and also encourages water borne disease which rots the roots. For this reason, rockwool slabs should only be lightly dipped into a nutrient solution - capillery action does the rest. Note that the acidity of rockwool is not the same as the acidity of the nutrient solution it comes into contact with. For most plants, recommendations already compensate for this fact but please take this into account when growing delicate plants requiring specific acidity. If in doubt, please contact Esoteric Hydroponics regarding this matter.

Rockwool slabs are available in multiple sizes and in multi packs, such as the bundle of two dozen slabs pictured above.