How to Create a Monotub Mushroom Fruiting Chamber
How to Build a Monotub Mushroom Fruiting Chamber
A monotub is one of the most popular and effective DIY mushroom fruiting chambers for home cultivators. This step-by-step guide will show you exactly how to build your own monotub setup with readily available materials.
What is a Monotub?
A monotub is a modified plastic storage container designed to create the perfect environment for mushroom fruiting. It provides controlled air exchange, humidity, and light – all essential factors for successful mushroom growth. The beauty of a monotub is its simplicity and effectiveness, making it ideal for beginners and experienced growers alike.
Materials You'll Need
Essential Supplies:
- Clear plastic storage container (54-66 quart/50-60 liter size)
- Power drill
- Drill bits: 1/4", 1/2", and 2" hole saw
- Polyfill (polyester fiberfill/pillow stuffing)
- Micropore tape (paper medical tape)
- Fine-mesh screen material
- Sharp utility knife or scissors
- Duct tape
- Measuring tape or ruler
- Permanent marker
- Optional: Black spray paint or black plastic liner
Tools:
- Power drill
- Safety glasses
- Face mask (for drilling)
- Clean work surface
Step 1: Selecting the Right Container
Your choice of container forms the foundation of your monotub:
- Size: A 54-66 quart (50-60 liter) container is ideal – large enough for good yields but manageable in size
- Material: Choose clear or semi-transparent plastic to monitor growth
- Shape: Rectangular containers with straight sides work best
- Lid: Ensure it fits securely but is easily removable
- Brand: Sterilite, Rubbermaid, or similar durable brands are recommended
Pro tip: Check that your container has a smooth bottom without ridges or bumps, which can make creating an even substrate surface difficult.
Step 2: Planning Your Hole Configuration
Before drilling, plan your hole layout:
Traditional Monotub Design:
- Side holes: 2 rows of 3-4 holes on the long sides, 2 rows of 2-3 holes on the short sides
- Lid holes: 4-6 evenly spaced holes
- Hole position: Side holes should be approximately 2-4" from the bottom and 3-5" from the top
Measurement Guidelines:
- Mark a line 3-4" up from the bottom of the tub (this will be above your substrate level)
- Mark another line 2-3" down from the top of the tub
- Space holes evenly along these lines, approximately 4-6" apart
- For the lid, mark 4-6 evenly distributed points
Top View of Monotub
Side View of Monotub
Basic monotub hole configuration diagram (green circles represent holes)
Step 3: Drilling the Holes
Now it's time to create the air exchange system:
Safety First:
- Wear safety glasses to protect from plastic debris
- Work in a well-ventilated area
- Secure the tub firmly when drilling to prevent movement
Drilling Process:
1. Side holes:
- Use a 1/4" or 1/2" drill bit for side holes
- Drill slowly to prevent cracking the plastic
- Keep the drill perpendicular to the surface
- Clean up any rough edges with sandpaper
2. Lid holes:
- Use a 2" hole saw attachment for larger lid holes
- Apply gentle pressure and let the drill do the work
- Hold the lid securely on a piece of scrap wood to prevent splintering
Pro tip: If you don't have a hole saw, you can heat a metal can of the appropriate diameter and use it to melt clean holes through the plastic.
Step 4: Preparing the Air Exchange System
Your monotub needs filtered air exchange while maintaining humidity:
For Side Holes:
Option 1: Polyfill Method
- Take small tufts of polyfill and gently stuff into each hole
- Adjust density for proper air flow:
- Too loose: excessive air exchange, low humidity
- Too tight: insufficient fresh air, potential for high CO2
- The polyfill should protrude slightly on both sides of the hole
- Aim for medium resistance when pushing air through
Option 2: Micropore Tape Method
- Cut pieces of micropore tape approximately 2" square
- Apply over each hole, completely covering it
- Use two layers in an "X" pattern for added strength
- Press firmly around the edges to ensure a good seal
For Lid Holes:
- Cut mesh screen material into squares approximately 3" × 3"
- Place over each 2" hole
- Secure with duct tape around the edges
- Cover with a looser polyfill stuffing than the side holes
Pro tip: For micropore tape application, cut the tape before removing the tub's manufacturer labels. Apply tape over holes, then remove labels to avoid adhesive issues.
Step 5: Light-Proofing the Bottom (Optional)
Light-proofing prevents side pinning and directs mushroom growth upward:
Method 1: Spray Paint
- Measure up about 4-5" from the bottom
- Apply painter's tape along this line around the entire tub
- Spray paint the bottom portion black
- Apply 2-3 light coats rather than one heavy coat
- Allow to dry completely (24 hours) before use
Method 2: Liner Method
- Cut a black plastic garbage bag to fit inside the tub
- Line the inside bottom and lower sides
- The liner will naturally pull away from the sides as the substrate shrinks, creating a microclimate that discourages side pinning
Step 6: Adding Handles (Optional)
For easier handling of your monotub:
- Drill two 1/2" holes on opposite short sides, approximately 2" down from the top edge
- Thread a strong rope or nylon cord through the holes
- Tie secure knots on both ends to create handles
- Ensure the handles are tight and can support the weight of a full monotub
Step 7: Creating a Light Diffuser (Optional)
For species that benefit from diffused light:
- Cut a piece of translucent white plastic (like a shower curtain) to fit the inside of the lid
- Secure it with small pieces of tape
- This diffuses light evenly across your growing surface
Step 8: Final Assembly and Testing
Before using your monotub:
- Clean the entire tub thoroughly with a 10% bleach solution
- Rinse well and allow to dry completely
- Secure all components and check that the lid fits properly
- Test air flow by blowing gently through the side holes
- Ensure all holes are properly covered with their filtering material
Monotub Variations to Consider
Unmodified Monotub
No holes drilled. Lid simply flipped upside down during fruiting to create a gap. Simplest design but offers less environmental control.
Shotgun Monotub Hybrid
Additional holes drilled in the bottom. Sits on risers over a humidity tray. Provides more passive air exchange.
Dubtub
Uses two identical tubs. One tub holds substrate, the other serves as a high dome lid. Good for mushroom varieties that grow tall.
Tips for Monotub Success
- Build multiple tubs: Having 2-3 monotubs allows for experimentation with different designs and provides backup if one fails
- Consistent conditions: Place your monotub in a location with stable temperature
- Cleanliness: Wipe down your monotub with alcohol before use
- Air exchange adjustment: Learn to adjust polyfill density based on growth patterns
- Measure twice, drill once: Take your time with measurements before creating permanent holes
How to Use Your Monotub
Your monotub is now ready for use! Here's a quick overview of how to use it:
- Add 3-4" of prepared, colonized substrate to the bottom
- Secure the lid and keep in a warm location during colonization phase
- Once fully colonized, adjust polyfill/airflow for fruiting conditions
- Maintain proper humidity and fresh air exchange
- Harvest mushrooms as they mature
- After harvesting, the monotub can be used for multiple flushes
Conclusion
Building your own monotub is a rewarding project that creates an effective, low-maintenance fruiting chamber for mushroom cultivation. This design has proven successful for countless home mycologists and, once built, can be reused for many grows to come.
With your monotub constructed, you're ready to move on to the exciting process of growing mushrooms. Your new fruiting chamber will provide the perfect environment for turning colonized substrate into beautiful flushes of mushrooms.
About Out-Grow.com: We provide high-quality mushroom cultivation supplies and expert guidance for growers of all experience levels. From spawn to substrates, we have everything you need to start or expand your mushroom growing journey.