Hydrofarm Rockwool Block Covers 4" Pack of 40 special-order and the controller unit does

and the controller unit does the rest

Cell trays are specifically designed to help your seedlings form proper root systems and allow for proper drainage to avoid mold issues

You safeguard your crop by avoiding calcium or magnesium deficiencies

multi-purpose growing medium that contains a mycorrhizal inoculum (Glomus intraradices)

review historical climate charts

Hydrofarm Rockwool Block Covers 4" Pack of 40 special-order and the controller unit doesDescription Product Details: Block light from media Reflect light to plant leaves where it's needed most Eliminate algae and mildew growth 40 dual sided block covers per pack Specifications Barcodes: 10638104945780 (GTIN) 638104945783 (UPC A) Dimensions: 5. 4L x 5. 2W x 5. 6H (CS) 5. 5L x 4. 5W x 0. 3H (EA) Shipping Weight: 0. 16 lbs.