good question i want to know this too homebrewer because if i can find a different rockwool that drains faster than i could probably still use itHey homebrewer are you using the B'CUZZ blocks? I'm using the Grodan as well and my blocks have been wet for 4 days under my 1K hps. It looked like that 's what you're using when i was following the GH vs DG thread? If so i'm guessing they must be different forms of RW? You said that yours will dry out in a day with no plant, mine would probly stay wet for a week under no light. Curious to know what the differences are.