Your purchase includes one bag of Growstone hydro stones™ (enough to fill 5 plant pots) and a sample of Zymbac™.



Product Description

Growstones aggregates are engineered to provide an effective ratio between aeration and moisture to any hydroponic system. While other substrates maximize either air or moisture, Growstones are designed to allow for both moisture absorption and drainage.

Most important in any growing medium is the air in the medium after drainage. Plant roots require air (particularly oxygen) for growth process respiration.

Growstones aggregates make for an ideal hydroponic substrate due to its small and large pores.  When the substrate is irrigated, water is held in the micro pores but quickly drains through the macro pores, allowing fresh air to flow through the substrate, which brings oxygen to the roots and removes carbon dioxide from the root zone.

Growstones Hydroponic Medium Give You:

  • Highly effective balance between air and water content at field capacity, meaning high air-filled porosity coexist with high water holding capacity.
  • Growstones hold 3 times more water and 12% more air than Hydroton.
  • Easy control of root zone moisture content – high steer-ability.
  • Easy drainage and re-wetting after being completely dehydrated.
  • Silica release in a form plants can uptake.
  • Highly flexibility for different plant needs for consistent high yield.
  • No weed seeds or disease spores.
  • Reusability and lightweight.
  • A sustainable and earth-friendly option.


Recycled Product

Growstones are manufactured using up to 98% waste materials. They replace mined materials like pumice, perlite, clay pellets, and stonewool, reducing environmental degradation. At the same time, since the product largely consists of recycled glass bottles, a large amount of glass waste is given a new life, keeping it from the landfill.

Download Growstone 101: Everything you need to know about Growstones

Download Technical Data for GS-1 Hydro Stones

Download GS-1 Hydro Stones Sell Sheet


“I wish I never stocked Hydroton because Growstone is our best-selling product.”

– Dave, Seattle Hydro Spot, Seattle, Washington


Getting Started



At home or in the greenhouse, Growstones are an ideal substance to grow a wide variety of crops in different hydroponic systems. Growstones can be used in systems as simple as manually irrigated containers, or as advanced as automatically irrigated systems such as drip irrigated containers, Ebb-Flow, and NFT tables.

For first time use, rinsing might be necessary to eliminate any dust created during shipping.

1.   Poke small holes at the bottom of the bag. Open the top of the bag and insert a garden hose and let drain.

2.   Place Growstones in your hydroponic system with pH-corrected nutrient solution. For best results adjust water or nutrient solution to pH to 5.5 – 6.5.

Planting Seedlings In Growstones 

Whichever your hydroponic system may be, follow these simple steps for planting in Growstones:

  1. Fill your growing container with Growstones half way up. The size of the container should be proportionalto the expected final size of the plant. For example, tomato plants develop a dense root system to sustain a lush and relatively large plant, thus a container size between 5 and 15 gallon is recommended to avoid root bound issues.
  • Ebb-flow systems

Fill container with a volume of Growstones proportional to your recirculating pump. Nutrient solution should rise until Growstones feel moist to touch 1” to 2” below the surface.

  • NFT systems

Total depth of Growstones should be adequate to support and keep root crown above water level.

  • Containers

Fill container with Growstones to within 1” from the top.

  1. Whether you germinated your seedlings or just bought them in a seedling tray, now its time to plant them into Growstones. Gently detach the seedling plugs from the seedling tray, keeping the substrate attached to the roots.
  2. Place the plugs at the center of your container just above the Growstones. If the container is large and wide enough you can place two plugs per container.
  3. Fill the rest of the container around the seedling plug with Growstones up to 1” to 2” below the edge of the container.
  4.  Irrigate immediately after planting to promote contact between the new substrate and roots.

Note: For Ebb-Flow systems, due to Growstones’ lightweight, it is important to use completely wet Growstones, in order to keep pots from tipping sideways during initial water Ebb-flow cycles, when plants are very small.  This is not an issue in other hydroponic systems.


How To Plant a Baby Basil Seedling into Growstones


Suggested Irrigation

As a rule of thumb, irrigate to maintain the surface of Growstones moist to touch about 1” below the substrate surface.

NFT systems

Maintain thin film of nutrient solution flowing at all times.


For recently transplanted seedlings, irrigate once to twice a day. Irrigate until drainage is visible from bottom of container and frequent enough to maintain Growstones moist to touch about 1” below the surface at all times.

Manual Irrigation

Manual irrigation in Growstones is generally recommended for low water usage plants such as aromatic herbs, perennials or short cycle vegetable plants grown in individual containers. Irrigate thoroughly until drainage is visible at bottom of container and frequent enough to maintain substrate moist to touch about 1” below the surface at all times.


How To Reuse Growstones

Growstones are a reusable plant-growing medium. To reuse Growstones in a second crop, simply remove old plant material from the container and shake vigorously to displace most of Growstones attached to roots. If necessary, to get rid of the root ball, as is the case for crops with strong roots such as tomatoes, simply cut the base of the stem at the root ball level, and remove the root ball. Some Growstones aggregates will be clinging tightly to these roots and might be lost. Some finer roots actually grow into the aggregates and might remain attached to the media, but most will fall out. Add some new Growstones to replenish the system and replant again by repeating steps 2 through 4.

As with any media, it is recommended to sterilize the previously used Growstones to eliminate any pest or disease that may be present before reusing the Growstones in another crop. When available, steam sterilization is the most recommended method. Growstones can be steam sterilized without losing physical integrity. Alternatively, Growstones can simply be tilled into soil to improve soil texture and structure.


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