These boxes just arrived today 
Grodan was kind enough to send me about 6,000 GBI (Grow Block Improved) GR4 blocks for free for my cloning test. The GR4 block is 3" x 3" x 2.5" and hole-free.
I’m testing cloning in the GR4 blocks so I can seamlessly transition to my two-ish week veg using ebb/flow (not drip) before up-potting to GBI GR22.5 (6 “x6” x4") for flowering. I’m simply going to stack each GR4 on top of a GR22.5 for a total root volume of 2.73 liters. I’m going to use three 0.33 GPH Netafim drippers in flowering. One dripper in each GR4 and two on the upward slope side of each GR22.5. In flowering, every grow rack tier will be filled with a different strain, greatly simplifying automated drip irrigation control and crop steering.
I’m doing this to avoid up-potting and drip-staking thousands of Grodan A-OK rooting cubes into GR6.5 blocks for two-ish weeks in veg. Just to de-stake, move, up-pot, and re-stake thousands of GR6.5 blocks two weeks later for flowering.
Plus, with ebb/flow, it is easy to ensure each strain gets enough water without overwatering. Which isn’t easy or cheap when using automated drip irrigation (Growlink) when each grow rack tier will hold six or more strains in the veg phase.
This should save majorly on labor costs and the PITA factor.
