Coco Coir Mushroom Substrate

Our Coco Coir Substrate brick is the go-to bulk substrate for monotub mushroom grows. Just add boiling water, let it hydrate and cool, mix it with your colonized grain spawn, and layer it into your monotub. No pressure cooker, no sterilization, no complicated prep.

Why Growers Use Coco Coir Substrate for Monotubs

Coco coir substrate is one of the most popular bulk substrates for monotub grows because it is forgiving, consistent, and easy to prepare. For beginners, this removes one of the most common failure points in the grow process.

• No sterilization needed: hydrating with boiling water is enough, no pressure cooker required.
• Holds moisture well: stays moist without becoming waterlogged.
• Neutral pH: naturally neutral, ideal for mycelium.
• Low contamination rates: the low nutrient content keeps contamination low while still giving your mycelium a moisture-rich environment to colonize and fruit from.

Substrate Specifications

How to Prepare Your Coco Coir Substrate Brick

What you need:

• 1 Coco Coir Substrate brick
• Boiling water
• Large bowl or bucket

Step 1: Hydrate the brick

Place the brick in a large bowl. Pour boiling water over it and break it apart as it softens. Use roughly 3 to 4 liters of boiling water per brick.

Step 2: Cover and pasteurize

Stir well until fully broken up. Cover the bowl with a lid or foil and let it sit for 1 hour. The heat passively pasteurizes the substrate.

Step 3: Check field capacity

Let it cool to room temperature. Squeeze a handful firmly. You want just a few drops to come out. If it drips heavily, let it dry a little longer before using.

Step 4: Mix with colonized grain spawn

Once cooled, mix it with your colonized grain spawn and layer it into your monotub.

How to Use Coco Coir Substrate in a Monotub

Once your grain spawn jars are fully colonized, hydrate the brick and mix it with your spawn at a ratio of roughly 1 part spawn to 3 parts substrate. Pack evenly into your monotub, seal it up, and let the mycelium finish colonizing the bulk layer before switching to fruiting conditions.

Not sure how much you need? Use our CVG calculator to work out the perfect substrate mix.

Frequently Asked Questions

Do I need to sterilize coco coir substrate?

No. Hydrating with boiling water and letting it sit covered for an hour is sufficient preparation. No pressure cooker needed.

Can I mix coco coir with vermiculite?

Yes. Many growers use a 50/50 coco coir and vermiculite mix. The vermiculite improves water retention and air exchange in the substrate. Our brick works well with this method.

How much does one brick make?

One brick expands significantly once hydrated and typically fills a standard monotub when mixed with grain spawn.

Can I reuse the substrate after a harvest?

Some growers reuse their substrate for a second or third flush by rehydrating and maintaining humidity. Results vary depending on contamination levels after the first harvest.