Bulk tub - DIY - Monotub mushroom grow how to

There are several techniques for growing mushrooms using monotubs, and new methods continue to be added every day. We’ll examine one of the simpler to set up techniques in this article.



Commonly associated with the cultivation of Magic Mushrooms or Shrooms, particularly Psilocybin Cubensis and other Psilocybe species that are well-suited for manure, this technique can also be used to grow the edible Coprinus comatus or Shaggy Mane mushroom. If you decide to change the bulk substrate to wood chips from manure-based, you could then grow oyster mushrooms from the Namekos and Pleurotus family.

Items needed for this technique

  1. Latex gloves

  2. Gorilla tape or any other suitable alternative

  3. A dark color plastic tray with a lid large enough to easily contain all of the growing substrate

  4. A spore or culture syringe

  5. A mushroom grow bag

  6. A fully colonized grain spawn (You don't need the syringe and sterilized grow bag if you already have this)

  7. A hand-drill with a two-inch hole saw

  8. A spray bottle for water

  9. A spray bottle for alcohol

  10. Poly-fil, tyvek, micropore tape or cotton balls to cover all the holes you drill

  11. A bottle of 70% rubbing alcohol

  12. Bulk substrate. This could be hardwood-based wood chips or manure-based substrate. It depends on the species of mushroom


Optional items/upgrades - Not required

  1. An LED light bar

  2. A Cycle timer

  3. A fan

  4. A humidity regulator

  5. A humidifier or fogger with a flexible hose



First Step: Prepare the mushroom grain spawn

You can buy mushroom grain spawn or you can make your own. As you have seeds for certain plants, you have grain spawn for mushroom growers. Grain spawn is grain that has been sterilized and colonized with the use of mushroom mycelium.

If you are growing a popular edible mushroom variety, you can purchase the colonized grain spawn.

colonizedbag.jpeg These colonized grain spawn can be used to grow nameko, oyster mushrooms etc. But the substrate in the tub will change depending on the mushroom specie you use.

If you decide to grow other species of mushroom that aren’t common, you may not find their fully colonized grain spawn for sale and you may need to make your own.


Here are the steps to follow to make your own fully colonized grain spawn.

First, you’ll need a sterilized grain bag. The bags will contain hydrated and sterilized millet, rye or another grain. 


Take a sterilized grain bag and inject 2.5ml of culture syringe through the injection port. Do this in a very clean location. It is important to create a very clean environment for this as the process is highly delicate. It's best to sterilize your hands, the inoculation surface, the injection bag and the syringe needle. Rubbing alcohol will work for sterilization. Wear your pair of latex gloves throughout the process. Examine to ensure there are no micro-cracks in the bag. 

Let your sterilized grain bag become colonized in a cool location. It shouldn’t be under direct sunlight. The temperature should not drop below 55F and it shouldn’t rise above 85F. The warmer it is within this range the faster growth will be. After a few days you’ll start to see white mycelium growing on the grain. The white mycelium will shoot outward from the injection point. Let it grow to about 75%, then break up the colonized grain without opening the bag. Mix the colonized grain into the grain that hasn’t been colonized. This will hasten the colonization process.

Once your bag is full of white mycelium, 0112211000a.jpg the mushroom spawn is ready for usage. This could take a few weeks to a few months depending on the species of culture used.


Second Step: Buy or Make Your Bulk Substrate

The contents of your bulk substrate depend on the type of mushroom that you want to grow in your tub. If you want to grow manure-loving mushroom, this step is for you. 

You can buy ready made manure substrate that has already been cooked and sterilized. With ready made manure substrate, you do not need to gather ingredients and spend time mixing them together.

But if you decide to make your own manure substrate,  you can go for an easy combo of 50% horse poo and 50% coco coir. You can get horse manure from stables and farms around you. Ask for horse manure that has been composted for at least 6 months. That is the best. You can get coco coir from gardening or hydroponic shops.

Mix the coco coir, and the horse manure together and get the mixture hydrated to field capacity. Take a handful of the substrate and squeeze it. You should be able to get at least one or two drops of water. Any more than that and you have a mixture that is over-hydrated. You should add more coco coir to thicken it. If a handful of the mixture can’t yield one or two drops of water, then it is under-hydrated. You need to add water slowly to it while testing it at the same time.

The bulk substrate can be pasteurized by steaming or cooking in an oven. To steam it, put the substrate in filter patch bags and steam it in a pressure cooker to about 160 or 180F. To cook it, preheat the oven to 170F and cook the substrate using baking pans. Wrap the baking pans with a tinfoil cover and cook for about two and a half hours.

Let the substrate cool down before using it.


Third Step: Prepare the Monotub

There are several methods of making a monotub. The most common container used is the large plastic Rubbermaid, Sterlite or Tupperware containers. Mushrooms are phototrophic, or sensitive to light when growing, and they will grow towards the direction of the light. In an equally dimly lit area each mushroom might grow it's own direction.


The lid of the bin should allow light in so the mushrooms grow upward. Mushrooms that grow towards the bottom or side are difficult to harvest and will waste your time, energy and the nutrients provided by the substrate. Be sure to select a container that includes a lid and is very dark in color.  Alternately you can simply add a contractor type trash bag to a clear container with some tape. This will let the mushrooms grow as they should and make them easily harvest-able for you.


Now, here is how to prepare the monotub in details


You need some holes in the bin for it to breathe. This is where the drill comes in handy. Get a drill with a two-inch saw. Use the drill to create some holes around the upper half of the bin. You should have about one hole for every eight-inch length of bin. Ensure that the holes are evenly spaced around the upper half of the bin. The holes should be above the substrate that will be in the bin. You can improvise and use other tools to make holes in the bin if you don’t have a drill.

Fill up the holes you have drilled with poly-fil or cover with Tyvek. Pol-fil stops particles in the air from entering the substrate while ensuring that the substrate breaths. Use gorilla tape to seal the poly-fil so it won’t pop out.

Now, the monotub is ready.


Fourth Step: Sterilize the working space and tub

This step is very important so you need to be very careful here! The whole process needs to be done carefully. Get some of the rubbing alcohol into a spray bottle and spray the alcohol to sterilize the whole tub. Spray your hands, working surface, scissors and any other tool you’ll be using going forwards. Spray the outside of the bulk substrate bag and the spawn bag.

Ensure that you are in a very clean room. Vacuum the room and wait for some time, so that the particles in the air will settle down.

Close and seal up all windows and doors. You don’t want dirt to enter through any medium.


Fifth Step: Transfer the bulk substrate into the tub and inoculate it

The amount of spawn and bulk substrate to use depends on the size of the tub you have with you. The substrate should be about three to five inches high in the tub. A 3-pound bag should be able to inoculate one or two moderately sized tubs.  

Ensure that the bulk substrate at field capacity. Repeat the test you carried out earlier and check the moisture content of the substrate. If a handful of substrate can’t yield one or two drops of water, then you can add a little sterilized water to the mixture as you fill the tub.

Break up the colonized grain substrate and add the manure based substrate to the tub of colonized grain. Mix them together well.  Once mixed lightly press the surface of the substrate down with the flat of your hands to ensure good contact between the colonized grains and the new manure substrate. 


Cover the bin. 

Keep the bin out of direct sunlight in a place that is a bit warm, aim for about 80 deg. f. for faster growth. 


Sixth Step: Check the bin for signs of full colonization

Inspect the sides of the bin to watch for signs of colonization. You’ll start to notice white spots that expand from every point of grain spawn. Later, the white spots will cover the entire surface of the substrate. Small droplets will start to pop out. This is a good sign of fast colonization and proper hydration.

Check for pinning mushrooms. Pinning mushrooms grow vertically from the surface of the bulk substrate while forming small knots of white mycelium. mycpinclose.jpg

For manure substrate, the tub will take about two or three weeks to fully colonize. For hardwood, the colonization rate varies.


Seventh Step: Harvest

Once you begin to notice hyphae pins or knots monopin.jpgyou can remove the lid from the bin safely.

Spray the tub with water every day and open the lid of bin a little bit so that some oxygen can get into the tub. Ensure that the bin gets enough ambient light so the mushrooms grow in the right direction. As said earlier, light helps mushrooms to grow in the right direction.

Once the mushrooms get to a stage that you want them, you can harvest them. Most mushroom species are ready to harvest just before the caps flatten out. wp-20190325-17-32-52-pro.jpg