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Cubensis Substrate Recipe — The CVG Method for Dung-Loving Mushrooms

When growers search "cubensis substrate recipe," the answer is almost always CVG — coir, vermiculite, gypsum. CVG is the de-facto bulk substrate for every dung-loving (coprophilous) species, and it's the formula behind nearly every popular bulk tek you'll find in research literature. This guide gives you the exact recipe by grams, the field-capacity hydration math, pasteurization windows, and the variables that actually matter for clean colonization and heavy fruiting.

Legal & Educational Notice

This article is published for educational and research purposes. Psilocybe cubensis is a controlled species in many jurisdictions, including the United States at the federal level. CVG itself is a generic horticultural substrate used for many legally cultivated species (Wine Cap, Almond Agaricus, paddy straw mushrooms, and others). Follow all local laws and regulations regarding fungi cultivation in your area. Rhizofunga does not sell Psilocybe spawn, cultures, or spores.

What CVG Is (And Why It Works)

CVG stands for Coir, Vermiculite, Gypsum. It's a non-nutritious, well-buffered bulk substrate that mimics the moisture and pH profile of dung — which is why dung-loving species colonize it aggressively and resist contamination during pasteurization (rather than full sterilization).

  • Coco coir — fibrous, water-retaining matrix. Provides physical structure and consistent moisture release.
  • Vermiculite — expanded mineral that holds 3–4× its weight in water and aerates the mix.
  • Gypsum (calcium sulfate) — buffers pH around 6.5–7, supplies trace calcium and sulfur, and discourages anaerobic pockets.

Why this works without sterilization: CVG is low-nutrient. Most contaminants need sugars and proteins to compete; the spawn brings its own colonized food source (grain) and rapidly outpaces airborne molds in a substrate with little for them to eat.

Exact CVG Recipe (by Weight)

The classic ratio is 2 : 2 : 1 (coir : vermiculite : gypsum) by volume. By weight (which is what actually matters for hydration math), that translates to roughly:

Ingredient Small batch Standard batch Large batch % of dry weight
Coco coir (dry brick) 325 g 650 g 1,300 g ~52%
Vermiculite (medium grade) 275 g 550 g 1,100 g ~44%
Gypsum (CaSO₄·2H₂O) 25 g 50 g 100 g ~4%
Total dry weight 625 g 1,250 g 2,500 g 100%

Volumetric shortcut for memory: two parts coir, two parts vermiculite, one part gypsum. Some recipes call out 4 : 4 : 1 — that's the same ratio if you read carefully (2:2:0.5 simplifies to 4:4:1).

Hydration: Hitting Field Capacity

Field capacity is the sweet spot — the substrate holds the maximum water it can without dripping when squeezed. For CVG it's roughly 65–70% moisture content by weight. The math:

  • Standard batch dry weight: 1,250 g
  • Target hydrated weight at 65% moisture: ~3,570 g (≈ 3.6 L water added)
  • In practice: pour boiling water over the dry mix at a 1 : 2.5 (dry weight : water) ratio, lid on, let it steam for 1–2 hours.

The Squeeze Test

Once cooled, grab a handful and squeeze hard. You should see 1–3 drops of water trickle out. No drops = too dry; a steady stream = too wet (drain in a colander). This is the gold standard — more reliable than a moisture meter on a rough fiber substrate.

Pasteurization (Not Sterilization)

CVG is pasteurized, not sterilized. Pasteurization knocks back competitive molds and bacteria but leaves beneficial thermophiles and a microbial "ceiling" that helps your spawn outcompete contaminants.

  • Boiling-water steep (most common): pour boiling water over the mix, seal in an insulated container, hold above 160°F (71°C) for 60–90 minutes. Most home growers stop here.
  • Hot-water bath: submerge the substrate in 160–180°F water for 60–90 minutes.
  • Oven pasteurization: bagged substrate at 200°F (93°C) internal for 60 minutes.

Don't Sterilize CVG

Pressure-sterilizing CVG (15 PSI / 250°F) creates a biological vacuum. Without competing organisms, the first contaminant in wins — and you'll lose more bins to mold this way, not fewer. Save sterilization for nutrient-rich substrates like Master's Mix or grain.

Spawn-to-Substrate Ratio

For dung-loving species on CVG, the standard ratio is 1 : 2 (spawn : substrate) by weight. Higher spawn ratio = faster colonization but more contamination risk if the spawn is impatient. Lower ratio (1 : 4) is doable for experienced growers using fully colonized, healthy grain.

Substrate (hydrated) Spawn @ 1:2 Spawn @ 1:3 Tub size
2 kg / ~4.4 lb 1 kg / ~2.2 lb 670 g / ~1.5 lb 6-quart shoebox
4 kg / ~8.8 lb 2 kg / ~4.4 lb 1.3 kg / ~3 lb 32-quart tote
8 kg / ~17.6 lb 4 kg / ~8.8 lb 2.7 kg / ~6 lb 66-quart monotub

Colonization & Fruiting Parameters (General)

Parameters vary by species. For dung-loving species on CVG, the typical envelope is:

  • Colonization temp: 75–80°F (24–27°C). Stable temps matter more than hitting an exact number.
  • Colonization humidity: not critical — sealed tub holds plenty of moisture. Avoid opening for the first 7–10 days.
  • Time to full colonization: 10–18 days at 1 : 2 spawn ratio.
  • Fruiting temp: 70–75°F (21–24°C) for most coprophilous species. Some prefer cooler.
  • Fruiting humidity: 90–95% RH at the substrate surface.
  • Fresh air exchange (FAE): 4–6× per day, light fanning. Excess CO₂ causes long stems and small caps.
  • Light: 12 hours indirect or low-intensity LED daily. Triggers pinning and orients fruit bodies.

Pro Tips and Common Pitfalls

  • Use horticultural-grade gypsum, not drywall scrap. Drywall contains additives that suppress mycelium.
  • Coir from compressed bricks is more consistent than loose-bagged coir, which often has variable particle size and lingering coco dust.
  • Rinse vermiculite if it's dusty. Inhalation isn't a major risk with the food-grade horticultural product, but a quick rinse improves uniformity.
  • Don't over-mix after pasteurization. Once spawn is added, fold gently — breaking up grain lumps too aggressively wounds mycelium.
  • Casing layer is optional on CVG. A 1 cm layer of plain pasteurized coir + vermiculite (no gypsum) on top of the colonized cake can boost fruiting consistency in dry climates.
  • Cold shock is unnecessary. Fruit bodies pin in response to light, FAE, and humidity changes — not temperature drops. The "cold shock" myth comes from outdated literature.

Related Rhizofunga Guides

Sterile Workflow Gear

Bulk substrate work doesn't require sterile technique, but spawn prep and grain transfers do. Our automatic and hands-free sterilizer keeps your workflow moving.

Safety and Legal Notice

This article is for educational purposes only. Cultivation of fungi is regulated differently across jurisdictions; some species are prohibited federally and at the state level in the United States and elsewhere. Verify the legal status of any species you plan to cultivate before sourcing spawn or culture. Practice basic lab safety with hot water and pasteurization equipment.

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Frequently Asked Questions

CVG stands for Coir, Vermiculite, Gypsum. It's the de-facto bulk substrate for dung-loving (coprophilous) mushroom species — non-nutritious, well-buffered, and resistant to contamination during pasteurization.
Pressure-sterilizing CVG (15 PSI / 250°F) creates a biological vacuum. Without competing thermophiles, the first contaminant to land on the substrate dominates — and you'll lose more bins to mold this way, not fewer. Pasteurization at 160-180°F for 60-90 minutes kills competitive molds while leaving a beneficial microbial ceiling that helps your spawn outcompete contaminants.
1:2 (spawn to substrate) by weight is the standard for dung-loving species on CVG. A higher 1:1 ratio colonizes faster but increases contamination risk if your spawn is impatient. Experienced growers can run 1:3 or 1:4 with fully colonized, healthy grain — but only after they've nailed the basics.
The squeeze test is more reliable than any moisture meter on a fibrous substrate. Grab a handful and squeeze hard. You should see 1-3 drops of water trickle out. No drops means it's too dry; a steady stream means it's too wet (drain in a colander before using). Field capacity is roughly 65-70% moisture content by weight.
No. Drywall scrap contains additives and binders that suppress mycelium growth. Always use horticultural-grade or food-grade calcium sulfate (CaSO4·2H2O). It's inexpensive and widely available at garden stores or online.
No, a casing layer is optional. A 1 cm layer of plain pasteurized coir + vermiculite (no gypsum) on top of the colonized substrate can boost fruiting consistency in dry climates and helps with even pin formation, but it's not required. Start without one — many growers fruit straight from CVG with no casing.
10-18 days at a 1:2 spawn ratio for most dung-loving species at 75-80°F (24-27°C). Stable temperature matters more than hitting an exact number — fluctuating temps slow colonization more than a slightly cool stable environment does. Avoid opening the tub for the first 7-10 days to keep humidity high and contaminants out.
75-80°F (24-27°C) is the sweet spot for most coprophilous species during colonization. After full colonization, drop to fruiting temperature (typically 70-75°F / 21-24°C). For temperature stability, place tubs on a heat mat with a thermostat — ambient room temperature is rarely consistent enough for fast, even colonization.
No, cold shocking is unnecessary for dung-loving species on CVG. Fruit bodies pin in response to light, fresh air exchange (FAE), and humidity changes — not temperature drops. The 'cold shock' myth comes from outdated literature. Once colonization is complete, expose the substrate surface (open the tub, mist, fan), and pinning will follow within 5-10 days under proper conditions.