Introduction

Monotub is a very popular method of growing mushrooms, especially among beginning indoor growers. It is simple to make, quick, and does not require a sophisticated ventilation system or complex humidifiers. The principle is based on a perforated plastic tray equipped with filters to ensure air exchange while maintaining optimal ambient humidity. These conditions favor the colonization, pinning and fruiting of mushrooms.

Growing “piopino” style mushrooms

Although this technique is often associated with growing mushrooms in manure (such as Psilocybe cubensis), it is important to note that growing psilocibin mushrooms is illegal in many countries. This article does not promote it. Instead, we recommend growing edible mushrooms like oyster mushrooms, nameko mushrooms and piopino mushrooms. These lignicole species are ideal for experimenting with this method, simply adjusting the substrate according to the types of mushrooms you want to cultivate. This article has an informative purpose and aims to show how these mushrooms can be grown with simple and accessible techniques.

Necessary Materials

Here is the material needed to build and use a monotub:

• Transparent plastic tray. A 60 liter bin corresponds approximately to dimensions of 60 x 40 x 35 cm. This provides enough space for a substrate of 8 to 12 cm thickness and good ventilation.
• Drill with drill bits for drilling 2.5 cm and 5 cm holes.
• Microporous adhesive tape or filters to cover holes and limit contamination.
• Sterile substrate, suitable for the type of mushrooms you wish to cultivate (lignicolous substrates).
• Colonized or sterile grains (mycelium on grains available here).
• Spray spray to maintain humidity.
• Plastic sheet to create a liner at the bottom of the bin.
• Isopropyl alcohol to sterilize equipment and work surfaces.
• Nitrile gloves for handling sterile materials.

Choice of Substrate

The choice of substrate directly depends on the type of mushrooms you want to grow:

• Wood-loving mushrooms: such as namekos or piopinos. Use a substrate made from wood chips / sawdust like our optimal substrate. For oyster mushrooms, the organic straw pellets will work well.
• Coprophilous mushrooms: such as Agaricus. Use a substrate made from composted manure.

Growing “Piopinos” style mushrooms

At Mycosphere, we offer sterile organic substrates suitable for wood-decomposing fungi as well as mycelium on grains for inoculation.

Monotube assembly

To build an efficient monotub, here are the key steps:

1. Drill the holes: Most monotubs use Tupperware type bins. You can customize the size and location of the holes depending on the species of mushroom you are growing. In general :
   • Large holes (5 cm): Six holes are recommended, two on each long side and one at each end, approximately 20 cm from the bottom.
   • Small holes (2.5 cm): Positioned approximately 4 to 5 cm above the intended level of the substrate. These holes ensure good air circulation.

   To avoid cracking, start by marking the hole locations, then first drill a small pilot hole with a fine drill bit before using a suitable hole saw. One trick is to melt the holes using a drill in “reverse” mode. This limits plastic splintering and creates cleaner edges. You can also heat a blade to melt the plastic.

   Make sure you work in a well-ventilated area and wear a mask to avoid inhaling plastic fumes.

2. Clean: Sterilize the inside and outside of the tank with 70% isopropyl alcohol, as well as all your work equipment (scissors, spatulas, etc.).
3. Add a liner: Use a thick plastic sheet, ideally black, to cover the bottom of the bin. This reduces potential contamination and makes cleaning easier. Cut the sheet so that it perfectly fits the dimensions of the bottom, with a slight overhang on the sides.

Substrate Preparation

The substrate you will use depends on the species you wish to cultivate. This can be a mixture of coconut fiber and vermiculite, straw pellets, wood shavings, etc.

In all cases, you must moisten your substrate with the right amount of water (between 60% and 75%) and then sterilize or pasteurize it.

Example: If you have 1 kg of coconut fiber and vermiculite mixture that you want to humidify to 75%, you must add 3 kg of water for a total of 4 kg of humidified substrate. Note that the base substrate can contain a certain percentage of humidity, and that it is better to put a little less water at the start, even if it means adding it later if it is too dry.

For sterilization:

• In the pressure cooker: Place the moistened substrate in a heat-resistant bag and sterilize it for 90 minutes at high pressure.
• By pasteurization: Pour boiling water over the substrate placed in a container cleaned with alcohol. Cover and let cool. This will pasteurize it sufficiently to prevent contamination. This works very well with our organic straw pellets for example.

Once your substrate is prepared, you can move on to the next step: inoculation.

Liquid Crops and Sterile Grains

Liquid cultures are an effective method for introducing live mycelium into your substrate. They contain fragments of mycelium suspended in a sterile nutrient medium, providing rapid and uniform colonization compared to spore syringes.

Advantages of liquid cultures:

• Faster colonization because the mycelium does not need to germinate.
• Ease of use with sterile mycelium on grains bags equipped with injection ports.
• Reduction of contamination risks compared to spores.

Preparation and use:

1. Sterilization: Make sure your hands, syringe needle, and injection ports are thoroughly cleaned with isopropyl alcohol.
2. Injection: Inject 2.5 to 5 ml of liquid culture into a bag of mycelium on grains via the injection port.
3. Incubation: Place the bag in a clean, dark place at a temperature between 20 and 25 °C. After 1 to 2 weeks, you may see the mycelium starting to spread. At this point, you can gently shake the bag, while keeping it well closed, to distribute the mycelium throughout the entire mycelium on grains and accelerate the colonization process. The grain should be fully colonized in 2 to 4 weeks.

The colonized mycelium on grains bags are then ready to be integrated into your substrate in the monotub. Some simply use our sterilized mycelium on grains as a fruiting substrate (not for wood-loving mushrooms), and fruit them using the monotub box as a fruiting tent. In this case, there is no need to use another substrate. You just need to open the plastic bag where the mushrooms start to grow, and possibly remove the plastic completely if it is obstructive. The box will play a role in maintaining humidity. For this option, you can skip the next step of incubating the substrate.

Incubation

Place the monotub in a stable, temperature-controlled environment, ideally between 20 and 25°C, for a period of 2 to 3 weeks.

During this phase, check your tray daily. You will notice white spots gradually spreading from the mycelium on grains inoculated, until they completely cover the surface of the substrate. This indicates healthy and active growth. Droplets of exudate, an amber liquid naturally produced by the mycelium, may appear on the substrate, signaling good hydration and rapid colonization.

Also watch for signs of “pin” formation: small, vertical white hyphae developing in dense nodes, announcing impending fruiting. During this time, make sure humidity and temperature levels remain constant. Condensation on the lid and substrate is a good indicator of adequate hydration.

However, be alert for mold or unusual colors, which could signal contamination. Proactive management ensures optimal conditions for the growth and health of your mushroom crop.

The Casing Layer

Once the mycelium begins to form knots or "pins" on the substrate, it is time to add a layer of casing. This layer mimics forest leaves, creating an optimal environment for mushrooms to fruit.

Commonly used materials:

• Coir (coconut fiber)
• Peat
• Vermiculite (make sure it is certified asbestos-free)

Apply a thin layer of 1 to 2 cm of casing on the substrate and lightly moisten it using a sprayer. The layer should be well hydrated, but without excess water. Leave the lid slightly offset to improve air exchange and reduce CO risks₂ accumulated.

During this period, continue to spray with water daily and expose the monotub to indirect light. Although fungi do not photosynthesize, light is essential to guide their growth.

Mushrooms generally reach maturity within one to two weeks after the casing layer is added. Harvest them before their caps are fully open for best quality and flavor.

Fructification

Fruiting is a key stage in the mushroom cultivation cycle. Once the substrate has completely colonized, expose the monotub to indirect light to encourage fruit formation. Maintaining high humidity, between 90% and 95%, is essential to support mushroom growth.

Cultivation of white button mushrooms

Conditions optimales :

• Humidity: Regularly spray water inside the monotub to maintain humidity. Droplets on the substrate are a good indicator.
• Ventilation: Leave the lid slightly open or drill additional holes to improve air exchange and prevent accumulation of CO₂.
• Light: Soft, indirect light, about 6 to 12 hours per day, helps guide the growth of mushrooms.

Monitor fruiting: Check daily for the appearance of "pins" or young mushrooms. The first signs include white hyphae thickening into dense knots. These "pins" develop rapidly into mature mushrooms within one to two weeks.

Light condensation on the sides of the tray is normal and indicates adequate hydration. However, watch for signs of contamination, such as green or black mold.

Harvest: Harvest the mushrooms when their caps are still rounded and before they open completely. This ensures better quality and flavor. 

With proactive management and careful care, the fruiting phase will result in an abundant, high-quality harvest.