​What is a Shotgun Fruiting Chamber, and How Do I Build One?

​What is a Shotgun Fruiting Chamber, and How Do I Build One?

Posted by J&K at APN on Mar 03, 2021

Mushroom Fruiting Chamber DIY

How To Build A Shotgun Style Mushroom Fruiting Chamber

A shotgun fruiting chamber, or mushroom fruiting chamber, is simply a large clear tote with holes drilled into the sides, and wet perlite at the bottom.

Often called a sgfc, and named for the scattered ventilation holes reminiscent of a shotgun pattern. Shotgun Fruiting chambers are easy to build and need no special equipment. Once properly set-up, it will provide a nearly perfect flow of fresh air while maintaining the necessary humidity for mushroom fruiting. The clear allows natural light in, holes provide fresh air exchange, while the wet perlite slowly releases moisture, maintaining humidity.

Note: While a Shotgun Fruiting Chamber and a Monotub look alike, they serve very different cultivation methods. Check here for our DIY for easily building a mushroom monotub.

How to build a mushroom fruiting chamber

Requires basic tools and about one hour. 

Materials you will need

  • A clear tote with lid, roughly 50 quart size (locking lids work best)
  • 4 gal of Course Perlite (the larger sized the better)
  • Spray Bottle
  • Hygrometer (not needed, but helpful)
  • Power Drill
  • 1/4 inch to 1/2 inch drill bit
  • Measuring Tape
  • Sharpie Marker

STEP 1: Make your drill marks

Using your measuring tape and sharpie make a dot about every 3 inches on all 6 sides of the tub, including the top and bottom of the tub . This allows airflow to come from the floor and up though the perlite into the chamber once it’s filled.

Step 2 Drill, and drill, and drill...

Use your power drill and slowly drill out each and every dot. It’s boring, but it really only takes a few minutes.

STEP 3: Add glass, really!

Add 2-4 inches of perlite to the bottom of your newly created mushroom fruiting chamber. Soak the perlite with water until it begins to drain from the bottom holes. It’s best to do this outside or in a bathtub to allow the excess water to drain away

FYI: Perlite is a form of volcanic glass which expands rapidly when super-heated, creating large numbers of micro-pockets for water storage.

You have now successfully built your own Shotgun Style Mushroom Fruiting Chamber.

Shotgun fruiting chambers can be used for fruiting many kinds of colonized substrate, like Pf tek jars, Boom blocks all in one grow bags , bulk substrate , grain spawns, manure substrates and more.


Open and lightly fan the chamber at least twice per day. You are exchanging the stale air in the bottom of the tub for fresh air. After each fanning you will need to add some humidity back to the chamber by spraying the perlite surface. It’s easy to judge the humidity level in a shotgun fruiting chamber: If the sides of the chamber have droplets of water forming it’s good.

Spray until the sides have a few drops sliding down into the perlite to replenish the water content. It’s best to avoid spraying the mushroom substrate directly unless it appears dry.

TIP: An ultrasonic humidifier can exchange the air and keep the humidity correct at the same time. A small hose from the outlet to your chamber works great to maintain the environment.

Let there be (a little bit of) light!

Indirect natural sunlight is best for your mushrooms to grow. While fungi do not need light in the same way that plants do, they do need a little bit to grow really well. A few moments of light per day is plenty and to much light can be detrimental to the fruiting stage.

TIP: If you can see inside the mushroom chamber then there is enough light for the mushrooms to fruit. Most mushrooms will receive plenty of light as you fan and mist them so extra light isn’t needed.

Shotgun Fruiting chambers work great!

New and experienced cultivators alike employ these awesomely simple mushroom fruiting chambers for the best of reasons.

Now that yours is built, get growing!