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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, Shrooms, 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 non-transparent black contractor bag or black spray paint

  4. A spore or culture syringe

  5. A mushroom grow bag

  6. A fully colonized grain spawn (You don’t need the syringe and injection port bag if you 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. A Tupperware plastic bin

  11. Poly-fil

  12. A bottle of 70% rubbing alcohol

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


Optional items/upgrades

  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 specie, you can purchase the colonized grain spawn. These colonized grain spawn can be used to grow nameko, oyster mushrooms etc. But you need to understand that 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 rye. The injection port will work in conjunction with the culture or spore syringe.

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 have a sterile environment for this as the process is highly delicate. You must sterilize your hands, the inoculation surface, the injection port bag and the syringe needle. Rubbing alcohol will work for sterilization. Wear your pair of latex gloves throughout the process. Ensure that there is no tear in the bag, no matter how tiny it may seem. 

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, 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. But if you want to grow hardwood-loving mushroom species, you can get wood chips from hardwood trees like the maple wood, ash, rosewood and oak trees.

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 poo or 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. But you can make do with whatever that is available. 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 Tupperware containers. Mushrooms are sensitive to light when growing, and they will grow towards the direction of the light, even if the light is coming from the sides or the bottom of the light. Mushrooms that grow towards the bottom or side are tough to harvest and will waste your time, energy and the nutrients provided by the substrate. Line up the inside of the container with a contractor bag to blot out light or spray paint the lower half exterior of the container with black paint. This will let the mushrooms grow as they should and make them easily harvest-able for you.

If you have more money to spare, you can get fish totes. These fish totes are already dark so they won’t let in light around the bottom or sides. You’ll just modify the lid so some light will get into the bin.

Now, here is how to prepare the monotub in details

Buy a bin that comes with a lid.

Paint the lower half of the bin if it is transparent. This will block out light.

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. That is the part that hasn’t been painted or blocked out. 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. 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.

The lid of the bin should allow light into the bin so the mushroom grows towards the light. If you are using a transparent bin with painted sides and bottom, you are good to go. If you are using a fish tote, you’ll need to have a plastic window in the lid. You can cut out a 12-inch by 12-inch square opening into the lid, then use clear plastic to cover the opening, thus forming the plastic window. Use gorilla tape to hold the window in place.

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 injection port 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.

Don’t transfer all the bulk substrate at once. Start by sprinkling about one inch of bulk substrate into the sterilized tub. Add a tiny sprinkling of colonized grain spawn to the bulk substrate in the tub. Add another inch of bulk substrate followed by another thin sprinkling of spawn.

Continue to add layers of bulk substrate sandwiched with sprinklings of colonized grain spawn till your desired depth is reached.

Sterilize the lid of the bin with alcohol. Add some alcohol to a paper towel and use that to wipe down the inner sides of the tub that is above the inoculated bulk substrate.

Cover the bin. You can’t open the bin anymore till the bin has been fully colonized.

Keep the bin out of direct sunlight in a place that is a bit warm. You don’t want it somewhere that is hot. You just need a little warmth with some ambient light.


Sixth Step: Check the bin daily for signs of full colonization

Inspect the sides of the bin every day 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 of mushroom 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.

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


Seventh Step: Case the tub and wait for the mushroom to fruit

Once you begin to notice hyphae pins or knots, you can case the tub. Remove the lid from the bin safely.

Add about half-inch to one inch of coco coir to the bin and spray the bin with a little water until the casing starts to indicate signs of full hydration. You can also use vermiculite to case the monotubs, but some experts feel that this could cause some contamination. You’ll be fine with using coco coir alone.

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 light so it grows 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.