Grodan Rockwool Grow Blocks are an inert hydroponics growing media that is made from glass fibres.
Grodan Rockwool Grow Blocks are pre-drilled with a 40mm hole, which allows you to fit any type of propagation plug into the block to continue growing your plants in a hydroponic system like NFT or flood and drain.
Grodan Rockwool Grow Blocks should not be placed straight into your system once planted, you must wait for the roots to emerge from the bottom of the blocks, then remove the outer sheeting and place into your growing system.
Grodan Rockwool grow blocks can also be used with systems that use clay pebbles. The same applies, wait for your roots to emerge at the base and then remove the outer sheeting on the grow block and place into your clay pebbles.
Grodan Rockwool Grow Blocks are slightly alkaline and they should be pre-soaked in an acidic solution between 5.5 - 5.8 Ph for 24 hours before you use them.