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How To Build A Shotgun Fruiting Chamber (SGFC) in 5 Easy Steps

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We like to pick mushrooms. Unfortunately, mushrooms themselves are picky – and getting mushrooms to fruit properly requires that we present them with ideal growing conditions.

Building a Shotgun Fruiting Chamber (commonly referred to as an SGFC) is a quick and easy way to provide the perfect balance of fresh air and humidity that mushrooms demand.

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What is an SGFC?

A shotgun fruiting chamber is nothing more than a good sized clear tote, covered in holes, and filled with a few inches of wet perlite in the bottom.

The holes allow for fresh air and gas exchange, while the perlite serves as a way to maintain humidity. The tote should be clear in order to allow for an adequate amount of natural light to be passed through to your mushrooms.

a-simple-shotgun-fruiting-chamber-sgfc

A simple shot-gun fruiting chamber. The name comes from the hole pattern on the tote.

What is Perlite?

Perlite is a natural volcanic mineral that, when expanded, forms a coarse and porous granule with a large relative surface area. All the nooks and crannies in the perlite granules are able to hold water, which evaporates over time. This evaporation from the perlite is what allows for the high relative humidity in your fruiting chamber.

coarse-perlite-for-sgfc

A small pile of coarse perlite. You should be able to find it at your local garden center.

Building a Fruiting Chamber

Building a proper Shotgun terrarium won’t take too long at all, and only requires a few common tools. Once you get the materials you require, you should be able to build your SGFC in less than an hour.


Materials Needed

Tools Needed

  • A Power Drill with a ¼” bit
  • Measuring Tape
  • Sharpie Marker

STEP 1: Mark Out The Holes

In order to get proper air flow through the SGFC, you want to have evenly spaced holes on all 6 sides of your tote- including the lid and the bottom. General consensus is that spacing for the holes should be an even 2” grid. Mark out all your holes with a sharpie.

marking-out-the-holes

Mark out your holes spaced 2 inches apart in a grid.

lid-of-a-sgfc

Holes should be drilled on all 6 sides, including the lid and the bottom.

STEP 2: Drill The Holes

Using a ¼” drill bit, drill out all the holes you marked out. Make sure you don’t press too hard or else the tote will crack as you are pushing the drill through. You will also need to ream out the holes and make sure there are no shards of plastic stuck on the edge. This is a repetitive task, but shouldn’t take all that long.

drilling-the-holes-in-a-sgfc

Use a 1/4″ drill bit to drill all the holes. This takes a little while!

STEP 3: Fill The Bottom With Perlite

Fill the bottom of your SGFC with a couple inches of perlite. The exact amount doesn’t matter too much, just make sure that you have enough to evenly cover the bottom of the tote with a few inches.

You also want to make sure you use coarse perlite. If the grind is too fine, you will have a lot of perlite coming through the holes you drilled, making a mess of things. Fine perlite also won’t hold as much water as coarse perlite can.

soaking-the-perlite

The perlite should be wetted until it is thoroughly moist.

STEP 4: Soak Your Perlite

Soak the perlite by pouring water into your SGFC and mixing it around until the perlite is evenly moist. There is no need to soak it so much that water is pouring out the bottom of the tote. The intention is just to coat the perlite in water so that in can evaporate over time, increasing the humidity in your SGFC.

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STEP 5: Place Your Mushroom Block in the Fruiting Chamber

You now have a reasonably humid environment able to exchange gasses and receive fresh air- perfectly adequate chamber for growing all sorts of mushrooms on a small scale.

A typical use for a SGFC is to grow mushrooms using the PF technique, but you can just as easily use a shotgun terrarium with supplemented sawdust fruiting blocks, or even mushroom grow kits.

Although not entirely necessary, a hygrometer is a useful tool that can be placed in your fruiting chamber to help you monitor and manage the humidity levels. It will give you a really good idea of whether or not you need to spray the inside of the chamber. Over time, you will learn what humidity levels work best for different stages of the fruiting cycle.

a-mushroom-block-in-a-sgfc

A small mushroom block sitting in a humid fruiting chamber

How to use a Shotgun Fruiting Chamber

SGFC’s are almost maintenance free, but there are still some best practices you should follow when using the SGFC tek.

Fanning and Spraying

The holes on all 6 sides of your fruiting chamber provide a means for gas exchange, and allow for fresh air, but the holes alone are not enough. Once your mushroom blocks are placed in the chamber, you should be removing the lid and fanning in fresh air at least twice a day.

In order to keep the humidity up after fanning in dry air, you’ll need to mist your chamber. To do this, simply use a typical spray bottle, and thoroughly soak the inside walls and the perlite foundation with water.

Try to do this without directly spraying the mushroom block, as droplets of water on the mycelium or the mushroom fruit body can cause problems such as bacterial blotch.

a-spray-bottle-for-your-mushrooms

A simple spray bottle for misting your chamber.

Using a Hygrometer

A hygrometer is a useful tool to monitor the humidity in your grow chamber. Although not entirely necessary, it will help to give you an idea of whether or not you are providing an adequately moist environment.

Depending on the stage of the mushroom fruiting cycle, you’ll want your humidity to be in the range of 75%-90%. If the humidity drops too much, your mushrooms may have smaller, cracked caps, or may not even fruit at all.

It doesn’t matter if you can get a digital hygrometer or an analog one; just ensure that the range of the device is such that it can measure relative humidity all the way up to at least 90%. Some household hygrometers won’t accurately measure that high.

Look for the types of hygrometers that they use in humidors, which can accurately measure high relative humidity levels.

Lighting for Your Fruiting Chamber

Contrary to popular belief, most mushrooms do need adequate amounts of light in order to form proper fruiting bodies. However- they need this light for different reasons than other plants do.

The best location for your fruiting chamber is a place where it will receive natural indirect sunlight for most of the day. Direct sunlight will be detrimental to your grow, as it will heat up your growing chamber too much and may cause your mushrooms to abort.

Indirect natural light natural light is by far your best bet, such as near a window but away from the rays of the sun.

If you don’t have the option of providing natural light to your fruiting chamber, you could always supplement with artificial light. A good option would be to use a small florescent light on a timer, cycled 12 hours on and 12 hours off each day. This will simulate a natural light cycle.

If you choose this option, make sure that the light source is far enough away that it won’t overheat your chamber.

A Quick and Easy Solution

There are a million ways to build an elaborate growing chamber- with automated humidifiers, powerful fans and tons of space- but there is definitely nothing wrong with using a shotgun fruiting chamber to start.

Although they are simple and easy to build, they really do a great job of providing the ideal conditions mushrooms need to fruit properly. This makes the Shotgun Fruiting Chamber a great choice for new growers looking to learn, or even experienced growers who want a quick and easy grow chamber for running experiments.

Thanks for reading! Feel free to let us know of your experience with SGFC’s in the comments below.

-spread the spores-

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olukunle ALABETUTU
olukunle ALABETUTU
3 years ago

Thanks for the write up, think the most challenging work is maintaining humidity for people in the tropic.Keep it up

Justin
Justin
3 years ago

Great write up. I just got into this, I am getting my first kit in the mail tomorrow and I’m anxious to get started. I have spent all my free time the last 5 or so days reading up on the process. I have been wondering about a good way to keep the environment right for the fruiting block and it looks like I just found it. I plan on trying a few different kinds, I am mostly interested in Reishi and Lion’s Mane, but also in something that can produce a lot of fruit.

Mark
Mark
3 years ago

Thanks for the detailed writeup!

Eric
Eric
3 years ago

I’m wondering if the bin size you link to will hold 12 half-pint cakes?

Sam
Sam
3 years ago

Is there any possible alternative to drilling holes with a power drill?
Maybe a knife, or ice pick, or burning holes with a lighter/hot poker…?

Sean
Sean
1 year ago
Reply to  Tony

when using plastic totes, drilling tends to crack the plastic either by to much pressure on the bit or as it punches through. I use a butane torch and a 1/4 inch metal rod I sharpened a point on…I then heat up the rod, an easily melt a hole through the plastic. not only does this ensure I don’t crack the plastic, but it also cauterizes the edges of the holes so they don’t crack after the hole has cooled. Just remember to do this outside, or in a well ventilated area with a respirator. The fumes are noxious…but the method works GREAT!

aschwetz
aschwetz
3 months ago
Reply to  Sam

Blowtorch and a metal rod works well. Similar to heating a coffee can on a stove burner to punch arm holes when making a Still-Air Box. Go slowly to avoid cracking the plastic.

Sorcha
Sorcha
3 years ago

The photo of the grain bag above is a bit confusing. How is the fully colonized bag supposed to fruit if its still in a bag? Do you need to open the bag? What about adding substrate?

Valeriy
Valeriy
2 years ago

Hi Tony
First of all what you are doing with this site is incredible! Thank you!
This is exactly what I need right now 🙂 I’m waiting for my first kit with Lions Mane mushrooms.
For this occasion I purchased 120 qt plastic tote. But I’m a bit concerned about drilling the holes.
It will be sitting on the wired shelf so I can’t drill the holes on the bottom of the tote and not sure about drilling too many holes in general in order not to lose the humidity. What if I add ventilation with the computer fan, with air movement from the top to the bottom close to one of the sides? Theoretically it should work. Should I turn it on/off with the intervals or leave it working continuously?
Or I shouldn’t be concerned about the humidity loss and just go and drill the holes on all sides but the bottom?
Thank you

Anthony
Anthony
2 years ago

Hey toney,
I was just wondering if you think it’s absolutely necessary to have a transparent lid on my fruiting chamber?

Chris
Chris
2 years ago

Hi,

How do you stop the perilit from falling out the bottom holes?

Do you use micro pore tape or something similar?

Chris
Chris
2 years ago

I’m thinking of using a spare 50gal aquarium as a chamber…I plan on attaching a fan to a piece of hosing with holes drilled to exhaust Co2 as well as one set the same way only backwards to pull in fresh air. These will both vent and pull thru a plexi lid. Is this a bad idea

donald howett
donald howett
2 years ago

Great site. I have built three fruiting chambers for our annual organic gardening event. I am growing 6 varieties of mushrooms in these chambers. Block instructions say to leave block in bag, soak for 24 hours, them place near window and mist daily. In the fruiting chamber the high humidity is more consistent. Is it still necessary to soak block for 24 hours prior to placing in container? Instructions say to slit bag on one side only , but presumably with 5 sides exposed to environmental conditions inside chamber you could slit bag on all sides?
Do you need the bag at all if you cover the block with a fruiting cap of peat and perlite?

Jim
Jim
2 years ago

Hi! Thanks for this great write up!

I am going to built such a chamber, but I wonder about the possible odors that come with fruiting mushroom (Oysters for now). Does it smell? My girlfriend doesn’t like mushroom and wishes I would put this tote outside the house because she fears mushroom odors. (Canada) I am concerned about bugs that could come in the tote if I put it outside. Could I make less holes to the side (say, 2-3 rows) and top and cover the holes with tyvek or autoclave fabric (blue SMS fabric) to prevent bugs to get in but still have some air exchange? There would still be holes at the bottom but I guess it’s less problematic for bugs to get if I lift the tote 4-5 inches off the ground.

Thanks in advance for your input!

Justin Raper
Justin Raper
2 years ago

Does tote have to be clear?

Elizabeth
Elizabeth
2 years ago

Do you continue misting and fanning after pins form? And if so, at the same rate?

James
James
2 years ago

Hi tony.

Do you have any suggestions on how to keep the fruiting box at an adequate temperature. It currently winter in my corner of the globe and I am looking at growing some warm climate mushrooms such as golden oyster.

Thanks

Ben
Ben
2 years ago

If I placed this in a larger tub. Could I just simply add water to the larger tub to a point below the substrate and let it soak into the perlite through the holes In the tub?as well as constantly keeping the perlite wet it would provide alot of humidity.

Myron
Myron
1 year ago

Hi Tony,
I was given a large flow hood, but the only place I think of to place it is in the barn/ open work area. Will this be ok or should I build a room to accommodate.

Chester
Chester
1 year ago

Hi Tony, Thanks very much for sharing your information. I am only just starting out and your site has helped me massively already.
I was wondering if it is possible to grow 2 different mushroom types in the same Shotgun Container or should they be kept well away from each other?
I have made some PF Tek cakes, 4 X Lions mane and 4 X blue oyster. I would like to experiment with growing a variety of Fungi in the future but cant find much information about growing different types near each other.
Any advice from you or anyone else would be greatly appreciated

Larry
Larry
1 year ago

I’m gonna try fruiting trays inside my SGFC. I’ve been successful with trays inside a monotub, but I’m curious to see if trays will fruit well in my SGFC as well.

Jamie
Jamie
1 year ago

Hey There Tony,
I am a first time grower and all your videos have really made this new adventure so exciting. I purchased some liquid culture to inoculate some sterilized rye grain. I have already constructed my SGFC but I am still unsure of when to place the block in the chamber. Do I wait until the bag is completely white or can I put it in the fruiting chamber immediately after inoculation? I find your videos the easiest to understand, so I thought maybe you could help me! Thanks a bunch for your time – Jamie 🙂

Nick
Nick
1 year ago

hello, can you give me an idea of what temperature range I`ll need for fruiting?

pitriot
pitriot
1 year ago

Lot this post. Helped me a lot.
I do have a question. The Perlite you linked to in Amazon is super coarse type with sizes the size of a pea and as much as 1/2″. Is this the right type of Perlite?

Brenton
Brenton
1 year ago

Another solid write-up. So, what would the next step be for the at-home hobbyist, who wants to grow 1-2 mycobags at a time and doesn’t want to spend every day fanning and misting?

terpsryan
terpsryan
1 year ago
Reply to  Brenton

You could spawn to bulk using a monotub. Meaning when the mycelium blocks have fully formed, open the bags, cut the blocks up and put it in another substrate lol inside a Monotub, certain monotubs are self sufficient so very little maintenance

Raymond
Raymond
8 months ago

Tony, great article (a noob question) do you drill holes on the bottom? I read people say that is a must and then use another chamber underneath filled with water to keep the top chamber temp up. I have a warm enough area when I do not need a water filled camber, so are holes on the site by the Perlite good enough? Do you need holes on the bottom?

Steve
Steve
7 months ago

Hi there, thanks for all the info. I’ve just started looking into things as my first attempt without research failed miserably lol. I was just wondering if it could be possible to use sponge instead of perlite?

mizizzle
mizizzle
6 months ago

Thanks for the great information! Can you really just place the bag of substrate plus mycelium directly on top of the moist perlite? Is that not a problem for the bags? I would think direct contact with the moisture might cause a problem for the mycelium/mushroom growth.

mizizzle
mizizzle
5 months ago
Reply to  mizizzle

Ah, I suspect that if you only slit the top/sides of the bag and NOT the bottom then the moisture from the perlite won’t be a problem for the mycelium.

Any thoughts on why some pins seem to have aborted (they are hard) while others are growing nicely? Could pins dry out if the hole in the bag is too big? Next time i have a big-ish hole I’ll add tape around the edges to reduce it’s size.

David
David
5 months ago

Great article.
I live in the tropic.
Sometimes air temperatures in my area can reach up to 35°C(95°F).
How can I keep the temperature in sgfc cool enought for the mushroom to grow properly?

MrNason
MrNason
5 months ago

When I have been able to grow a solid mycelium I have had marginal growth in the fruiting chamber. My chamber is typical but I have it mounted over a tub of water. In the tub are humidifiers sending moisture to the perlite above, and adding warmth. It seemed clever but with poor results and where I live, as we are heading toward hotter and drier temps
(high temperatures and low humidity) I need a solution for my lack of fruiting!!

Shaul Strait
Shaul Strait
4 months ago

hey tony great article i rlly learned alot i am about to try growing mushrooms for the first time and was wondering if a led light will work for an indoor grow

Hiker Huggs
Hiker Huggs
3 months ago

Hey lovvvve your site and youtube vids! You are helping so much with my newbie setup. One question that I didnt see addressed for the SGFC. Can you re-use the perlite for another round of blocks? Or do you swap it all out once youve fully fruited and harvested all your flushes? If you can re-use, how many cycles ya think? Thanks again big fan of your teachings, I like your laid back approach and support for the “do what works best for you” mentality!