What is a Monotub and How Do I Build One?

A monotub is a type of container or fruiting chamber used in the cultivation of mushrooms, particularly species like Psilocybe cubensis, which are popular among home cultivators. The purpose of a monotub is to provide an ideal environment for mushroom fruiting, ensuring proper humidity, temperature, and air exchange. Monotubs are relatively simple to build and are an effective way to grow mushrooms in a controlled environment.

Here are the basic steps to build a monotub:

1. Materials:

   • Plastic storage tub with a lid: Choose a clear or translucent plastic tub that is around 60-80 quarts in size. The lid should be airtight.
   • Substrate: Prepare your mushroom substrate in a separate container, which typically consists of a mixture of vermiculite, brown rice flour, and water. This is where you will inoculate with mushroom spores or mycelium.
   • Spawn: You'll need mushroom spawn to inoculate your substrate. This can be purchased or prepared by growing mycelium on a grain or other nutrient medium.
   • Plastic liner: Line the inside of your tub with a clear plastic liner or trash bag to help maintain humidity.

2. Prepare the substrate:

   • Mix your substrate ingredients thoroughly in a large mixing bowl until you achieve a uniform consistency.
   • Fill the bottom of the monotub with 2-3 inches of the substrate mixture.

3. Inoculate:

   • Add your mushroom spawn to the substrate layer, spreading it evenly.
   • Cover the spawn with more substrate mixture, usually about 1-2 inches deep.

4. Create a microclimate:

   • Spray the substrate surface lightly with water to create a moist microclimate.
   • Place the lid on the tub to retain moisture.

5. Fruiting chamber setup:

   • After inoculation, the tub needs to be placed in a suitable location with indirect light, typically at temperatures around 75-80°F (24-27°C).
   • You may want to put the tub on a shelf or rack to allow for airflow underneath.

6. Fanning and misting:

   • To encourage fruiting, open the lid periodically to allow fresh air in and close it again.
   • Mist the inside of the tub with water to maintain humidity, typically 90-95%.

7. Monitor and harvest:

   • Keep an eye on the development of mushrooms inside the tub. It may take several weeks for your mushrooms to grow to maturity.
   • Harvest mushrooms when they are mature but before they start to drop spores.

8. Repeat the process:

   • After harvesting, you can repeat the process by adding a new layer of substrate and inoculating it with spawn.

Building a monotub is a straightforward process, but it's essential to follow sterile techniques during the inoculation process to prevent contamination. Additionally, make sure to research the specific requirements of the mushroom species you are cultivating, as different varieties may have slightly different needs.