Pargro® Rockwool Slab — 9.5in x 8in x 4in — Single — Pre-Cut Hole — Carton Packaging

Stonewool Growing Slab for Precision Drip Hydroponics, 9.5x8x4in

Moving a rooted starter block into a stable, long-term growing medium is one of the more failure-prone transitions in a drip hydroponic system, since the receiving slab has to match the block's moisture and root-zone behavior almost exactly. Grodan Pargro Rockwool Slabs are engineered stonewool growing slabs built on Grodan's fiber technology, giving drip-to-waste and recirculating systems a slab with consistent density, drainage, and moisture retention from one unit to the next.

This 9.5in x 8in x 4in slab ships individually in carton packaging with a pre-cut planting hole already sized for a standard rockwool starter block or Gro-Plug, so it drops into a drip channel ready for transplant.

Key Features & Benefits

• Pre-cut planting hole — sized for immediate placement of a rooted starter block or Gro-Plug without on-site cutting.
• Engineered stonewool fiber structure — gives the slab consistent density and drainage so irrigation behaves the same way across every slab in a run.
• Chemically inert media — does not alter the pH or nutrient balance of the feed solution, so growers control the root zone through the nutrient program instead of the media.
• 9.5in x 8in x 4in format — sized for standard drip channel systems, with enough depth for roots to expand from the starter block into the full slab volume.
• Individual carton packaging — keeps handling and storage clean for growers ordering single slabs rather than full pallets.

Who Should Use This

This slab fits growers running drip-to-waste or recirculating drip systems who want commercial-grade stonewool at an accessible price point. It works equally well for a home grower running a handful of slabs or a commercial operation standardizing on Pargro across a larger drip system.

About Grodan

Grodan is part of ROCKWOOL Group, a global supplier of stone wool growing media for professional greenhouse and controlled-environment growers. The Pargro line applies Grodan's stonewool manufacturing process at a more accessible price point than its premium lines, while keeping the same engineered fiber structure.

Frequently Asked Questions

What is the difference between Pargro and Grodan's premium rockwool lines

Pargro uses the same ROCKWOOL Group stonewool manufacturing process but is positioned as a value-tier line for growers who want commercial stonewool performance at a lower price point. Both share the same engineered fiber structure and chemical inertness.

How do I set up this slab in a drip system

Place the slab in your growing channel with the pre-cut hole facing up, then pre-wet it with pH-adjusted water before use. Insert the rooted starter block or Gro-Plug into the pre-cut hole and connect drip irrigation to the block so roots grow down and out into the slab.

How should I prepare the slab before transplanting

Soak the slab in pH-adjusted water, target pH 5.5, ideally with a dilute starter nutrient solution, for several hours before transplanting. This saturates the stonewool fibers evenly and pre-conditions the slab's pH so roots are not shocked on contact. Let excess water drain before inserting the starter block.

Can this slab be reused for a second growing cycle

Most commercial drip operations use a rockwool slab for a single cycle because of pathogen management concerns in shared irrigation systems. After harvest, spent stonewool can be broken up as a drainage amendment, composted, or disposed of per local waste guidelines.

Is stonewool safe to handle

Yes, with normal precautions. Wear gloves when handling dry stonewool and avoid touching your eyes, since dry fibers can cause minor irritation. Wetting the slab before handling largely eliminates this issue.