The 20x20mm rockwool starting block is used here after the roots have grown through. Grodan rock wool has a neutral pH value and should be soaked and rinsed with pH values around 5.5 to 6.0 (never below 5!) Before starting breeding.

7.5×7.5×6.5 cubes with a small hole
Round hole D = 25mm H = 35mm
384 pieces per box