🥥 3 Ingredient Options
Coco Coir only, Coir with Vermiculite, or full CVG mix with Gypsum
🌱 CVG Substrate Calculator
Our CVG Calculator finds the exact amounts of Coco Coir, Vermiculite and Gypsum for your mushroom substrate. Enter your colonized grain spawn weight, choose your ratio, and get instant results. 100% Free, no signup required.
⚖️ 5 Spawn Ratios
From 1:1 to 1:5 with density and colonization speed guide
🌍 Metric and US Units
Switch between grams and ounces, mL and quarts instantly
🔒 100% Free
No signup, no hidden costs, use it as often as you need
Mushroom Substrate Calculator
1 : 1
Fastest
Highest density. Fastest colonization.
1 : 2
Fast
High density. Fast colonization.
★ REC
1 : 3
Balanced
Good density. Balanced speed.
1 : 4
Slower
Lower density. Slower colonization.
1 : 5
Slowest
Lowest density. Slowest colonization.
Coco Coir
Required
Base substrate. Perfect water retention and sterile field capacity.
Vermiculite
Optional
Prevents compaction. Better air exchange and moisture retention.
Gypsum
Optional
Stabilizes pH. Adds calcium and sulfur. Prevents clumping.
Formula: CVG — 100g Coir : 100g Vermiculite : 20g Gypsum : 750 mL Water
Note: The CVG formula uses boiling water for pasteurization. No pressure sterilization needed. Always wait until substrate is fully cooled before adding spawn.
How to Mix CVG Substrate
Follow these 8 steps after calculating your ingredient amounts with the CVG Calculator above.
1
Boil Your Water ~5 min
Bring the calculated amount of water to a full boil, either in a kettle or on the stove. The boiling water is what pasteurizes your substrate, so make sure it is at a rolling boil before adding it.
2
Combine Ingredients & Add Boiling Water ~10 min
Add all your dry ingredients (Coco Coir, Vermiculite, Gypsum) into a large pot or bucket and give them a quick mix. Then pour the boiling water over the mixture and stir well until everything is evenly saturated.
⚠ Use a large enough container! Coco Coir expands dramatically when hydrated. It can increase up to 8× its dry volume. A coco brick that looks small will fill a large bucket, so always go bigger than you think you need.
💡 This is pasteurization — no sterilization needed. Coco Coir is naturally resistant to competing organisms, so boiling water is more than sufficient. You can use coco coir bricks, loose coir or coco powder. All work equally well.
3
Cover & Wait 4–6 Hours 4–6 hours
Place a lid or foil loosely over your container and leave it to cool. During this time the coir will fully absorb the water and the substrate will cool down to room temperature. After 4–6 hours, put on gloves and mix everything thoroughly. The substrate should now be uniform, evenly moist and fully cooled.
4
Check Field Capacity ~2 min
Field capacity is the ideal moisture level for your substrate. At perfect field capacity, your substrate creates the right humidity inside a closed monotub so that you do not need to open and water it constantly.
The squeeze test: Take a handful of substrate and squeeze it as hard as you possibly can. Judge what comes out.
Too Wet
A stream of water drips out. Add dry vermiculite and mix again.
Perfect
Only a few drops come out. This is exactly what you want.
Too Dry
Nothing comes out at all. Mist with water, mix and retest.
5
Add Spawn & Mix ~5 min
Add your colonized grain spawn into the monotub and break it up completely into small individual grains with no large clumps remaining. Then add approximately two thirds of your CVG substrate and mix everything together thoroughly until the spawn is evenly distributed throughout.
💡 Work quickly. Minimize how long the substrate and spawn are exposed to open air. Sanitize your hands and all tools with 70% isopropyl alcohol before starting.
6
Add the Casing Layer ~2 min
Spread the remaining one third of your substrate evenly over the top as a casing layer. This top layer protects the surface, reduces contamination risk and can improve pin set density. Gently press it down to eliminate air pockets.
Is a casing layer required? It depends on the species you are growing. For many grows it is not strictly necessary, but it never hurts either. I always add one since the benefits outweigh the minimal extra effort.
7
Colonization Conditions 5–14 days
Seal or loosely cover the monotub and move it to a warm, dark location. Avoid disturbing it during colonization as mycelium does not like being moved. Check daily for signs of white growth spreading through the substrate. Once the surface is fully covered in white mycelium and small pins (tiny white dots) begin to appear, you are ready to switch to fruiting conditions.
Temperature
21–24 °C
70–75 °F optimal range
Duration
7–14 days
Varies by ratio, temp and spawn health
Light
Dark
No direct light during colonization
Fresh Air
Minimal
Limited FAE until fully colonized
8
Fruiting Conditions & Fresh Air Exchange Until harvest
Once your substrate is fully colonized and pins are forming, it is time to switch to fruiting conditions. The main trigger is simply removing the tub from the dark and placing it somewhere with ambient room light. Direct sunlight should be avoided, but otherwise light level does not matter much. If your monotub has holes plugged with polyfill or micropore tape, fresh air exchange happens automatically and you do not need to manually fan it. At perfect field capacity your substrate holds enough moisture on its own, so misting is usually not necessary either.
Temperature
20–23 °C
68–74 °F slightly cooler triggers pinning
Light
Any indirect
No direct sunlight, everything else is fine
FAE
Automatic
Polyfill or micropore tape holes handle this passively
Humidity
90–95%
Perfect field capacity keeps this stable without misting
💡 First flush timing. Most setups produce their first pins within 5–14 days of switching to fruiting conditions. Harvest individual mushrooms just before or as the veil underneath the cap begins to tear. Do not wait until after the veil breaks as potency and shelf life both drop quickly after that point.
After each flush: Remove any leftover stems or dead material, lightly mist the surface and let the substrate rest for a few days. Most CVG setups will produce 2–4 flushes before yields drop off significantly.
Frequently Asked Questions
CVG substrate is a bulk mixture of Coco Coir, Vermiculite, and Gypsum used for mushroom cultivation. This blend provides an ideal environment for dung loving mushroom species to thrive. You create it by mixing the dry ingredients with boiling water to reach proper hydration.
No, CVG substrate does not require pressure sterilization. Simply pouring boiling water over the dry ingredients provides enough pasteurization. This process kills harmful pathogens while keeping beneficial microbes alive. Always let the mix cool completely before adding spawn.
A casing layer is completely optional but can be highly beneficial. CVG substrate will initiate mushroom pinning on its own once fully colonized. However, adding a thin top layer of pure coir helps improve pin density, retains moisture, and lowers overall contamination risks.
Hydrated CVG substrate should be used within 24 to 48 hours of preparation. If you store it sealed in the refrigerator, it can last up to seven days before contamination risks increase. Dry ingredients kept in sealed containers in a cool place will last for several years.
Perfect field capacity is the ideal moisture level where your substrate holds maximum water without being waterlogged. Check it by grabbing a handful and squeezing firmly. Only one to three drops should fall. If a stream drips it is too wet. If nothing falls it is too dry.
Gypsum is not strictly necessary but is highly recommended for best results. It stabilizes the pH level to prevent the substrate from becoming too acidic during growth. It also adds essential calcium and sulfur while preventing the mixture from clumping into a dense mat.