The Complete Grodan Stonewool Guide for Cannabis (2026): A-OK Plugs, Gro-Blocks, Gro-Slabs, and the Precision Growing Reality

Grodan is the canonical commercial cannabis stonewool brand. The 2026 guide to A-OK plugs, Gro-Blocks, Gro-Slabs, conditioning, and precision crop steering.

A commercial grower came into the shop last spring switching his whole room from coco to Grodan stonewool. He'd heard the precision-growing pitch, bought a pallet of Hugo blocks and Gro-Slabs, transplanted his clones, and watched a third of them stall out within the first two weeks. He wanted to know if he'd gotten a bad batch. The stonewool was fine. The problem was conditioning: he'd planted into blocks straight out of the wrap without pre-soaking them to the right pH. Stonewool comes out of the bag alkaline, around pH 7 to 8, and if you plant into it without conditioning it down to roughly 5.5 first, the root zone sits too high for nutrient availability and young roots struggle. He soaked his next batch properly, the stalling stopped, and by harvest he was getting the uniformity and control that made him want to switch in the first place. That conditioning step is the single most common Grodan mistake, and it's the difference between stonewool working brilliantly and working against you.

Grodan is the canonical commercial cannabis stonewool brand, made by parent company Rockwool and in horticultural cultivation since 1969. Stonewool (the brand prefers that term over "rockwool" to distinguish the growing substrate from Rockwool's insulation products) is molten basalt rock spun into cotton-candy-like fibers and compressed into plugs, blocks, and slabs. It's almost entirely air and water-holding capacity, around 5 percent solid fiber, and it's completely inert: it holds no nutrients of its own and locks out nothing. Whatever you feed is immediately available to the plant or drains straight through, which is the entire point. Grodan is built around what the brand calls Precision Growing: total root-zone control, immediate feedback on every feeding decision, and the ability to steer the crop generative or vegetative through precise water-content and EC manipulation.

This pillar is the retailer's complete operational manual for Grodan in 2026. What stonewool actually is and why Grodan's version differs from generic rockwool, the full lineup mapped as a graduated propagation-to-harvest system (A-OK plugs, Grow-Cubes, Gro-Blocks, Hugo blocks, Gro-Slabs and Uni-Slabs), the conditioning and pH reality that trips up new users, water-content and EC crop steering, the GroSens monitoring suite, honest framing on who stonewool is for and who should run a more forgiving medium, and a head-to-head versus coco. We sell Grodan at Modern Farms alongside coco, soil, and the nutrients and meters any inert-medium grow depends on. The case below is the honest one.

The 30-Second Answer

Grodan stonewool is an inert, sterile growing medium made from spun volcanic rock fiber. It holds a large volume of water and oxygen, contains no nutrients of its own, and gives the grower total control over the root zone because everything the plant gets comes from the feed solution. The brand's system is graduated by size: you germinate seeds or root cuttings in A-OK starter plugs, transplant ("block on") into Gro-Blocks for veg, and set the blocks onto Gro-Slabs for flower. The same plant moves through three substrate sizes without ever disturbing the root ball.

The lineup, smallest to largest. A-OK Starter Plugs for germination and cuttings. Grow-Cubes and Grow-Chunks as loose propagation and transplant formats. Gro-Blocks (Improved) in sizes like GR6.5 (4x4x2.5") and GR10 (4x4x4") for the veg stage. Hugo Gro-Blocks (6x6x6") as the larger "final block" that carries big plants through harvest, with drainage channels at the base. Gro-Slabs and Uni-Slabs (Improved) as the flowering slab, featuring the Advanced Hydrophilic Binder and Wetting Agent for uniform water content and EC distribution across the slab. The GroSens suite is the sensor system that measures water content, EC, and temperature for precision irrigation.

The single most important operational fact: stonewool is alkaline out of the bag (around pH 7-8) and must be conditioned before use. Pre-soak blocks and slabs in pH-adjusted water (around 5.5, with a starter nutrient solution) before transplanting. Skip this and young roots stall. After conditioning, stonewool gives immediate feedback, any feeding mistake shows up fast and can be corrected fast, because nothing is buffered or locked out.

Buy Grodan if you're a commercial precision grower or serious hobbyist who wants a clean, inert, sterile, fully steerable medium with immediate feedback and unmatched repeatability between crops; if you run drip irrigation or hand-water with discipline; or if you want the seamless plug-to-block-to-slab propagation pathway. Skip Grodan (or choose coco or soil) if you want a forgiving, buffered medium that tolerates irrigation mistakes, if you don't want to manage pH and EC closely, if you dislike handling a medium that holds a lot of water and can stay wet, or if you have concerns about working with mineral fibers and prefer an organic substrate.

What Stonewool Actually Is (And Why Grodan Differs From Generic Rockwool)

Worth understanding the material before the lineup, because stonewool's physical properties are the entire reason it behaves the way it does.

How it's made

Stonewool starts as basalt rock (volcanic rock) and chalk, heated to around 3,000°F until molten, then spun into thin fibers, the same way cotton candy is spun from melted sugar. Air is injected during spinning, and the fibers are compressed and bound into plugs, blocks, and slabs. The finished product is roughly 5 percent solid fiber by volume; the rest is pore space that holds water and air. That high pore volume is why stonewool holds so much water while still retaining oxygen around the roots, the combination cannabis roots need for fast growth.

The inert, sterile advantage

Stonewool is completely inert and sterile. It contributes no nutrients, holds no cation exchange capacity, and is pathogen-free out of the bag. This is the opposite of soil (which buffers and feeds) and different from coco (which has cation exchange capacity that binds calcium and magnesium). With stonewool, the nutrient solution you feed is exactly what the plant gets. As one industry source puts it, stonewool "does not lock out any fertilizer," so whatever you feed has an immediate effect, and any feeding mistake can be immediately corrected. That immediacy is the foundation of precision growing: no buffer means no lag between your decision and the plant's response.

Why Grodan isn't generic rockwool

Two things separate Grodan from commodity rockwool. First, Grodan engineers different fiber types for different products and growth stages rather than cutting every size from one batch of wool. The fiber orientation and density in a propagation plug differs from a flowering slab because the plant's needs differ at each stage. Second, Grodan runs the highest density on the market, which the brand argues delivers greater structural integrity (the medium doesn't collapse under the weight of water and a mature plant), better oxygen retention over the crop cycle, and improved wicking and moisture dispersion that pulls roots into more of the medium. Low-density rockwool collapses as it gets heavy, squeezing out the air pockets roots need; higher density holds its structure.

The handling and safety note

Stonewool is a mineral fiber, and dry stonewool can release fiber dust when cut or handled roughly. Wet the medium before cutting, wear a dust mask and gloves when handling large quantities dry, and avoid tearing blocks apart unnecessarily. Once wet and in use, the fiber is stable. This is a normal commercial-cultivation handling practice, not a reason to avoid the medium, but it's worth knowing up front.

The Grodan Lineup, Mapped as a Graduated System

Grodan's defining structural identity is the graduated-size pathway: a plant moves from plug to block to slab without ever disturbing the root ball. Worth mapping cleanly because the sizes are designed to nest together.

Propagation: A-OK Starter Plugs, Grow-Cubes, and Grow-Chunks

• A-OK Starter Plugs: the small plugs for germinating seeds and rooting stem cuttings. Consistent porosity for fast, uniform root development. Designed to drop directly into the holes in Gro-Blocks once roots show, so the transplant is seamless. The standard starting point for both seed and clone propagation.
• Grow-Cubes: loose stonewool in cube form, used for propagation and as a transplant medium that can be combined with blocks and slabs across different growth phases or irrigation methods.
• Grow-Chunks and Cress Plate: additional propagation formats. Grow-Chunks are a chunked loose-fill format useful for amending or filling containers; the Cress Plate is a propagation tray format.

Propagation is where stonewool's sterility and uniformity pay off most: clean, pathogen-free plugs give high strike rates on cuttings and even germination on seed, and the uniform porosity means every plug roots on roughly the same schedule, which keeps a production cycle on time.

Veg: Gro-Blocks (Improved)

• Gro-Block GR6.5 (4x4x2.5"): a starter block for the early vegetative phase, ideal for smaller plants or shorter veg cycles before transplanting up.
• Gro-Block GR10 (4x4x4"): the standard veg block, a common choice for the vegetative phase before moving onto a slab for flower.
• The "Improved" designation: Grodan's current-generation blocks feature the Advanced Hydrophilic Binder and Wetting Agent that improve how uniformly water and EC distribute through the block and how quickly the block re-saturates after it dries down. Uniform water content across the block means uniform root development.

An A-OK plug with rooted cuttings drops into the pre-formed hole in the top of a Gro-Block. The block carries the plant through veg, and when it's time to flower, the whole block sets onto a slab. The root ball is never disturbed.

Larger plants and final block: Hugo Gro-Blocks (6x6x6")

• Hugo Gro-Block (6x6x6"): the popular larger block for growing bigger plants. The Hugo is often used as a "final block" configuration that carries plant growth all the way through harvest without a slab, particularly for growers running fewer, larger plants. It has special drainage channels at the base to promote full drainage and uniform planting holes that seat plants at the optimal depth.

The Hugo is the choice when a grower wants a self-contained block big enough to finish a plant, or when running a lower-plant-count, larger-plant layout where a full slab system isn't necessary.

Flower: Gro-Slabs and Uni-Slabs (Improved)

• Gro-Slabs (Improved): the flowering slab, a long wrapped slab of stonewool that blocks sit on top of for the flowering phase. The Improved Gro-Slabs feature the Advanced Hydrophilic Binder and Wetting Agent for more uniform water content and EC distribution through the slab, faster re-saturation, and a wide control range for precision irrigation and crop steering.
• Uni-Slabs: a slab variant offering the same precision-irrigation control range, designed for reliable, easy irrigation across the slab.

The slab is where crop steering happens. The slab's large water-holding volume and the uniform distribution of the Improved binder let a grower run wide swings in water content and EC to push the plant generative (toward flowering and bulking) or vegetative (toward growth), which is the core of precision growing in flower.

Monitoring: the GroSens suite

• GroSens: Grodan's sensor system that measures water content (WC), EC, and temperature directly in the slab or block. Precision growing depends on knowing the actual root-zone conditions, not guessing, and GroSens gives the real-time readings that let a grower steer the crop accurately. For commercial operations running precision irrigation strategies, the GroSens suite is the feedback loop that makes the steering possible.

What this map gets you

A propagation-to-harvest pathway in a single medium: A-OK plug for germination or cuttings, Gro-Block (GR6.5 or GR10) for veg, then either set the block on a Gro-Slab for flower or move to a Hugo block as a final block. The plant never has its roots disturbed, the medium stays inert and steerable the whole way, and GroSens gives the readings to manage it precisely. The graduated system is the reason Grodan dominates commercial propagation and precision cultivation.

The Conditioning and pH Reality (The Step That Trips Up New Users)

The single most common Grodan mistake and the reason some growers conclude stonewool "doesn't work" when the problem is operational, not the medium. Worth a dedicated section because getting this right is the difference between stonewool working brilliantly and working against you.

Why conditioning is required

Stonewool comes out of the bag alkaline, typically around pH 7 to 8, because the basalt and binder leave a high baseline pH. Cannabis wants a root-zone pH around 5.5 to 6.0 for nutrient availability. If you transplant into unconditioned stonewool, the root zone sits too high, several nutrients become less available, and young roots stall or struggle. Because stonewool is inert and unbuffered, it won't self-correct the way soil would; it sits wherever you leave it.

How to condition blocks and slabs

Pre-soak the stonewool in pH-adjusted water before transplanting:

• Mix a starter nutrient solution at low-to-moderate EC (a light veg-strength feed) in RO or low-EC water.
• Adjust the solution pH down to around 5.5. Stonewool will pull the soak-water pH up initially as it releases its baseline alkalinity, so you may need to re-adjust during the soak.
• Saturate the block or slab fully. For slabs, the plastic wrap encases the product and acts like a bag: fill the wrap with solution until the slab is thoroughly wet, let it sit, then cut a drainage slit in the bottom of the wrap only after the slab is fully saturated.
• Let the conditioned medium sit saturated for several hours (overnight is common) so the pH equilibrates to target.
• Check the runoff or slab pH before transplanting; it should read in the 5.5 to 6.0 range. Re-soak if it's still high.

The plastic wrap is your friend

Leave the plastic wrapping on blocks and slabs. The wrap retains moisture, keeps light off the root zone (preventing algae), and on slabs it enables the initial pre-soak by holding the solution like a bag until the slab is saturated. Cut drainage slits only after the medium is fully wet, and only the slits you need. Over-handling or unwrapping the medium creates problems rather than solving them.

The immediate-feedback payoff

Once conditioned, stonewool's inert nature becomes the advantage that precision growers prize. Because nothing is buffered or locked out, the medium gives immediate feedback: feed an EC that's too high and you'll see it fast; correct it and the plant responds fast. There's no soil buffer masking your decisions and no coco cation exchange binding your calcium. You're feeding the plant directly, and the plant tells you immediately whether you got it right. That immediacy is exactly what makes stonewool unforgiving for careless growers and ideal for precise ones.

Water Content and EC Crop Steering

The reason commercial precision growers choose stonewool over more forgiving media. Crop steering is the deliberate manipulation of root-zone water content and EC to push the plant toward vegetative growth or generative (flowering and bulking) responses. Stonewool's large, uniform, controllable water-holding volume makes it the ideal medium for it.

What crop steering means

Plants respond to root-zone stress and abundance. Generally, keeping the medium consistently moist with moderate EC steers the plant vegetative (toward leafy growth), while letting the medium dry down further between irrigations and running higher EC steers the plant generative (toward flowering, fruiting, and bulking). Commercial growers steer vegetative during early veg and the stretch, then steer generative through flower to drive bud development and density. The wider the controllable range of water content and EC, the more steering authority the grower has.

Why stonewool steers well

Three properties make stonewool the precision-steering medium:

• Wide water-content range: a slab can be run very wet or dried down substantially, giving a broad range to work within. The Improved Gro-Slabs are specifically engineered for a wide control range.
• Uniform distribution: the Advanced Hydrophilic Binder and Wetting Agent distribute water and EC uniformly through the slab, so the whole root zone experiences the same conditions and every plant on the slab steers together.
• Fast re-saturation: the Improved medium re-wets quickly and evenly after a dry-down, so the grower can run aggressive dry-back-and-refill cycles without dead spots.

The dryback strategy

The core steering tool is the overnight dryback: how much the slab's water content drops between the last irrigation of one day and the first of the next. Small drybacks keep the plant vegetative; larger drybacks steer generative. Growers use the GroSens water-content reading to target a specific dryback percentage each day, tightening or widening it to steer the crop through the flowering cycle. This is a commercial-grade strategy that depends on accurate measurement, which is why the GroSens suite and stonewool go together.

The EC side

Running EC alongside water content compounds the steering effect. Higher feed EC plus larger drybacks concentrates salts in the slab and pushes hard generative; lower EC plus smaller drybacks keeps things vegetative. Because stonewool is inert, the slab EC reflects exactly what you fed plus what's concentrated by dryback, with no medium buffering to muddy the reading. Cross-reference: our EC and pH reservoir management guide covers the measurement discipline that crop steering depends on.

Grodan Stonewool vs Coco Head-to-Head

Coco is the natural comparison: the other major soilless medium, and the one most growers weigh against stonewool. The decision comes down to control versus forgiveness.

What they share

Both are soilless media that separate the medium from the nutrition, both work with drip and hand-watering, both support high-yield commercial cannabis, both require feeding a complete nutrient solution (the medium doesn't feed the plant), and both are widely available in commercial formats.

Where Grodan stonewool wins

Total control and immediate feedback. Stonewool is fully inert with no cation exchange capacity, so the feed solution is exactly what the plant gets and feeding mistakes are immediately visible and correctable. Coco's cation exchange binds calcium and magnesium and buffers the feed, which adds forgiveness but reduces precision.

Crop steering range. Stonewool's wide, uniform, fast-re-saturating water-content range gives more steering authority than coco. For commercial precision growers running dryback strategies, stonewool is the more controllable medium.

Sterility and uniformity. Stonewool is pathogen-free and uniform out of the bag, giving high propagation strike rates and consistent rooting schedules. Coco quality varies by brand and buffering, and lower-grade coco can carry salts or inconsistency.

The seamless graduated system. The plug-to-block-to-slab pathway moves a plant through the whole cycle without disturbing roots, which coco's container-based approach doesn't replicate as cleanly.

Where coco wins

Forgiveness. Coco's cation exchange capacity buffers the feed and holds a reserve of calcium and magnesium, so it tolerates irrigation timing mistakes and feed errors better than inert stonewool. For growers who can't irrigate with precision, coco is more forgiving.

No conditioning step. Quality buffered coco is closer to ready-to-use out of the bag (though it still benefits from a CalMag charge), while stonewool requires the pH conditioning soak that trips up new users.

Organic and renewable. Coco is a renewable coconut byproduct and an organic medium; stonewool is a mineral fiber. Growers who prefer an organic substrate or have concerns about mineral-fiber handling choose coco.

Re-wetting and dryout behavior. Coco re-wets easily even after drying, while stonewool that dries out too far can become difficult to evenly re-saturate. For hand-watering hobbyists with variable schedules, coco is more tolerant.

Disposal and handling. Used coco composts; used stonewool is a mineral product that needs disposal or recycling, and dry stonewool handling requires dust precautions.

The decision rules

Commercial precision grower running drip irrigation and crop steering: Grodan stonewool. The control and steering range are the whole point.

Propagation and cutting operations needing sterile, uniform, high-strike-rate plugs: Grodan A-OK plugs.

Hobbyist or grower who hand-waters with variable timing and wants forgiveness: coco.

Grower who prefers an organic, renewable medium: coco.

Grower who wants the lowest learning curve: coco (no conditioning step, more buffer for mistakes).

Grower chasing maximum repeatability and control between crops: Grodan stonewool.

Cross-reference: our complete coco coir guide covers the coco side of this comparison in full depth, including the buffering and CalMag reality.

The Honest Case For and Against

Buy Grodan stonewool if

• You're a commercial precision grower or serious hobbyist who wants total root-zone control and immediate feedback
• You run drip irrigation or hand-water with discipline and consistency
• You want to crop-steer through water-content and EC manipulation
• You run a propagation or cutting operation and need sterile, uniform, high-strike-rate plugs
• You value repeatability between crops above forgiveness
• You want the seamless plug-to-block-to-slab pathway that never disturbs the root ball

Skip Grodan stonewool if

• You want a forgiving, buffered medium that tolerates irrigation and feeding mistakes (choose coco or soil)
• You hand-water on a variable schedule and can't irrigate consistently
• You don't want to manage pH and EC closely
• You'd rather skip the conditioning step entirely
• You prefer an organic, renewable medium or have concerns about handling mineral fibers
• You dislike a medium that holds a lot of water and can stay wet if over-irrigated

The learning curve

The first stonewool cycle requires learning two things: condition the medium to pH 5.5 before transplanting, and irrigate with enough discipline that the inert medium doesn't stay waterlogged or dry out unevenly. After those, stonewool becomes the most controllable and repeatable medium available. The immediate feedback that punishes careless growers is exactly what rewards precise ones. Most growers who struggle with stonewool struggle with conditioning or irrigation discipline, not with the medium itself.

Specific 2026 Product Picks by Use Case

Modern Farms stocks the Grodan lineup.

Propagation and cuttings

• Grodan A-OK Starter Plugs (in sheets) for seed germination and cutting propagation
• Grodan Grow-Cubes for loose propagation and transplant flexibility
• Pair with a propagation dome and a dilute starter nutrient solution conditioned to pH 5.5

The veg-to-flower system (commercial drip, many plants)

• A-OK Starter Plugs for propagation
• Gro-Block GR10 (4x4x4") for veg
• Gro-Slabs (Improved) or Uni-Slabs for flower
• GroSens sensors for water-content and EC monitoring
• This is the classic commercial precision-growing configuration

The fewer-larger-plants layout

• A-OK Starter Plugs for propagation
• Gro-Block GR6.5 or GR10 for early veg
• Hugo Gro-Block (6x6x6") as the final block carrying plants through harvest
• The right pick when running lower plant counts with larger plants and wanting a self-contained block

The supporting equipment

• A quality pH and EC meter (a Bluelab combo or pen) is non-negotiable with an inert medium; you're flying blind without one
• RO or low-EC source water so you control the input chemistry (cross-reference our Hydrologic RO buyer's guide)
• A complete nutrient program formulated for inert/hydroponic media (Athena, Heavy 16, House and Garden, or the broader nutrient cluster)
• Drip emitters or a precise hand-watering routine
• GroSens or equivalent substrate sensors for serious crop steering

Cross-reference: our Bluelab buyer's guide covers the meters, the Hydrologic RO buyer's guide covers source-water treatment, and the EC and pH reservoir management guide covers the measurement discipline stonewool depends on.

Common Grodan Problems and Diagnostic Logic

"Transplants stalling in the first two weeks"

Almost always a conditioning failure. The blocks or slabs weren't pre-soaked to pH 5.5 before transplanting, so the root zone is sitting alkaline. Fix: always condition before transplanting. If plants are already in unconditioned medium, flush with pH-5.5 nutrient solution until the runoff reads in range and the root zone equilibrates.

"Medium staying soggy / roots looking unhealthy"

Over-irrigation. Stonewool holds a large volume of water, and if you irrigate too frequently the medium never gets the oxygen exchange a dryback provides. Fix: extend the interval between irrigations, allow a proper overnight dryback, and verify with a water-content reading. The medium should cycle between wet and a meaningful dry-back, not stay saturated.

"Slab or block dried out and won't re-wet evenly"

Stonewool dried too far can develop dry channels that water runs straight through, leaving dead spots. The Improved media re-saturate faster, but a severe dry-out still needs slow, repeated wetting. Fix: re-wet slowly with multiple small irrigations rather than one flood, and avoid letting the medium dry out that far again. Maintain a floor on your dryback.

"pH drifting in the slab"

Because stonewool is unbuffered, slab pH reflects your feed and what's happening at the roots. Drift usually traces to feed pH, EC concentration from dryback, or root-zone activity. Fix: verify and adjust feed pH to 5.5-6.0, monitor slab pH with runoff testing or a sensor, and adjust the feed rather than expecting the medium to correct itself.

"Algae or growth on the medium surface"

Light hitting wet stonewool grows algae. Fix: keep the plastic wrap on, cover exposed wet medium, and minimize standing water on top of blocks and slabs. Algae itself is mostly cosmetic but indicates light and moisture conditions worth correcting.

"Uneven plants across a slab"

Usually uneven water or EC distribution, often from emitter placement or a slab that wasn't uniformly saturated at the start. Fix: ensure even emitter placement and flow per plant, verify the slab saturated uniformly during conditioning, and use the Improved Gro-Slabs whose binder distributes water and EC more evenly.

Cross-reference: our EC and pH reservoir management guide contains the broader diagnostic flow for inert-medium feeding problems.

What We'd Tell You at the Counter

The honest summary, framed the way we'd say it face to face.

Grodan stonewool is the most controllable, most repeatable growing medium available, and that's exactly why it's the commercial precision-growing standard. The control comes with a tradeoff: stonewool is inert and unforgiving, so it rewards discipline and punishes carelessness. If you irrigate with consistency and manage pH and EC closely, stonewool will give you results and repeatability no buffered medium can match. If you can't, coco or soil will treat you more kindly.

Condition the medium before you plant into it. This is the one rule that matters most. Pre-soak blocks and slabs in pH-5.5 nutrient solution until the medium reads in range, and don't transplant into stonewool straight out of the wrap. The conditioning step is what separates growers who love stonewool from growers who give up on it.

Buy a meter and use it every feed. With an inert medium you're feeding the plant directly, so you need to know your pH and EC going in and ideally your water content and EC in the slab. A Bluelab combo meter and, for serious crop steering, GroSens sensors are the difference between precision growing and guessing.

Use the graduated system as designed. A-OK plug to Gro-Block to Gro-Slab, or a Hugo block as a final block for larger plants. The whole point is moving the plant through the cycle without disturbing the root ball. Don't fight the system by repotting.

Run a proper dryback. Stonewool steers beautifully if you let the slab dry back overnight and refill, and it goes soggy and oxygen-starved if you irrigate too often. The dryback is both your oxygen-exchange mechanism and your crop-steering tool. Learn to read it.

For propagation specifically, Grodan is hard to beat regardless of what medium you flower in. Even growers who flower in coco or soil often propagate in A-OK plugs for the sterility and uniform strike rates. If you take cuttings, the plugs are worth running.

The cluster of articles we've written reinforces this one. Our complete coco coir guide covers the forgiving alternative and the full medium comparison. The Bluelab buyer's guide covers the meters stonewool demands. The Hydrologic RO buyer's guide covers the source water you'll want to control. The EC and pH reservoir management guide covers the measurement discipline crop steering depends on. And the nutrient brand guides (Athena, Heavy 16, House and Garden) cover the complete feed programs that inert media require.

Modern Farms stocks the complete Grodan stonewool lineup: A-OK Starter Plugs, Grow-Cubes and Grow-Chunks, Gro-Blocks (GR6.5 4x4x2.5" and GR10 4x4x4"), Hugo Gro-Blocks (6x6x6"), Gro-Slabs and Uni-Slabs (Improved, with the Advanced Hydrophilic Binder and Wetting Agent), and the GroSens monitoring suite for water-content and EC sensing. We also stock the Bluelab meters, Hydrologic RO systems, and complete nutrient programs that inert-medium precision growing depends on. If you're switching to stonewool, dialing in a crop-steering strategy, or speccing a propagation-to-harvest system for a commercial room, we're happy to help in person or by phone. We don't upsell.

"This article is for informational and educational purposes only. Cannabis cultivation laws vary by state and locality. Grow only in accordance with the laws that apply to you, and where required, only as a licensed grower. Modern Farms sells equipment and supplies and does not provide legal advice."