Indoor monotub for year-round high-volume production

A monotub is a large plastic storage bin modified for airflow and humidity, allowing continuous indoor mushroom production regardless of season. Serious growers use monotubs to produce 5-15 lbs per month from a closet-sized space.

Steps

1. Modify a 66-quart clear storage bin: Drill six 2-inch holes — two on each long side, one on each short side. Stuff holes loosely with polyfill (pillow stuffing) for passive air exchange.
2. Prepare substrate: Pasteurize chopped straw or supplemented hardwood pellets (hardwood fuel pellets + wheat bran, 5:1 ratio) using the bucket hot-water method. Cool to below 80°F.
3. Spawn and pack: Mix cooled substrate with grain spawn (10-20% spawn rate). Pack firmly into the tub 4-5 inches deep. Close the lid.
4. Colonize: Keep the lid on, in a dark space at 70-75°F for 10-14 days until the surface is fully white.
5. Initiate fruiting: Open the lid slightly or flip it for increased airflow. Mist the sides of the tub (not the substrate directly) 2-3 times daily. Maintain 85-95% humidity.
6. Harvest and repeat: Cut mushrooms at the base when caps flatten. Rest 7-10 days between flushes. Each tub produces 3-4 flushes.

Tips

• Supplemented hardwood pellets (HWFP + bran) produce denser, meatier oysters than straw alone
• Run 3-4 tubs staggered 1 week apart for continuous weekly harvests
• A small USB fan on a timer (15 min on/45 min off) prevents CO2 buildup, which causes long stemmy mushrooms