How to Set Up a Monotub for Mushroom Cultivation: Step-by-Step

About 1 hour active work, plus colonization time

A monotub is a plastic storage bin with holes drilled in the sides, used to fruit mushrooms in bulk substrate. It is the most popular fruiting setup in home cultivation because it is cheap, scales to sizable yields, and forgives a lot of mistakes that would kill a more sensitive setup. This tutorial walks you through every step of monotub tek, from picking the right tub size to dialing in fresh air exchange after pinning.

By the end you will have a tub colonized with mycelium, pinning at the surface, and tracking toward a first flush in 18 to 30 days from inoculation. The technique covered here is sometimes called BOD monotub (bottom-of-dish or modified Bod), referring to the practice of running tubs without a casing layer and triggering fruiting via temperature drop and fresh air exchange rather than a soak. It is the simplest, highest-yielding starter setup that works.

What you'll need

Materials

Opaque plastic storage tub, 32 to 66 quarts (Sterilite Modular Latch is the community default)
Coir, 650 g brick (one standard compressed brick rehydrates to about 5 L)
Vermiculite, coarse-grade, 4 to 5 quarts dry
Gypsum (calcium sulfate), 2 to 3 tablespoons per tub
Boiling or near-boiling water, ~5 L for hydration
Colonized grain spawn, 4 to 6 quarts per tub (1:2 to 1:4 spawn-to-bulk by volume)
Synthetic polyfill stuffing, fist-sized clump per hole
Black contractor trash bag or matte black spray paint, for blacking out the bottom and lower sides
70% or higher isopropyl alcohol, plus a spray bottle
Filtered or pre-boiled water, for misting

Equipment

Cordless drill
1/2 inch to 5/8 inch drill bit (spade or step bit, both work)
Permanent marker, for marking hole positions
Large clean tote, 5 gallon bucket, or oven bag, for substrate hydration
Reliable thermometer
Min/max digital hygrometer (optional but recommended)
Spray bottle for misting

Step 1: Pick the right tub and drill it correctly

The tub is the single most important choice in monotub tek. Pick wrong and the rest of the tutorial fights you. Two requirements: opaque plastic (mycelium colonizes faster in the dark and side-pinning is much harder to control in clear tubs), and the right volume for the spawn you have on hand.

Tub size by spawn volume:

6 quart shoebox: better as a shotgun fruiting chamber, not a true monotub. Skip for this tek.
32 quart (e.g. Sterilite 1963): one quart jar of grain spawn into 2 to 3 quarts of bulk. Good first tub. Manageable, fast to colonize, low yield ceiling.
54 quart (e.g. Sterilite 1968): the most popular size by far. Two quart jars of grain spawn into about 4 to 5 quarts of bulk. Best balance of yield and consistency.
66 quart (e.g. Sterilite 1971): three quart jars of grain spawn into 6 to 8 quarts of bulk. High ceiling but harder to keep evenly humid; only attempt after you have run a 54 quart cleanly.

Get an opaque tub if you possibly can. If your only option is a clear tub, line the bottom and bottom 4 inches of every side with a black contractor trash bag, taped tight on the outside, or spray the lower portion with matte black paint. Blacking out the lower walls suppresses side pins, which form poorly, dehydrate fast, and steal energy from the main flush on top.

Drilling the holes: use a 1/2 inch to 5/8 inch bit. Anything smaller restricts fresh air exchange; anything larger dries the substrate too fast. Mark and drill holes in this pattern:

Six holes per long side, evenly spaced, positioned roughly 2 inches above the substrate line (which will sit at about 4 inches deep, so holes go around 6 inches up from the floor of the tub).
Three holes per short side, same height.
Four holes in the lid: one near each corner, also stuffed with polyfill.

That gives you 22 holes total on a 54 quart, which is a good starting density. Do not drill below the future substrate line. Holes in contact with wet substrate are bacterial entry points. If you guess wrong on substrate depth, drill a second row higher and seal the lower row with tape from the outside.

Safety note before you start drilling

Wear eye protection. Plastic tubs shatter unpredictably when bits bite, especially with cheap polypropylene. Drill at medium speed with light pressure; let the bit cut, do not push. Do the drilling outside or in a garage if you can; the dust is fine and unpleasant. Once drilled, wash the tub inside and out with hot water and dish soap, rinse thoroughly, then wipe down with 70% isopropyl alcohol before substrate goes in.

Stuff each hole with a fist-sized wad of synthetic polyfill (the kind sold for stuffing pillows and quilts). Polyfill is the filter: it lets gases pass and traps spores and dust on the way in. Pack it firm but not so tight that no air moves. You should be able to see daylight through the polyfill if you hold the tub up to a window. Replace the polyfill between grows, or wash it in a hot bleach soak and let it dry fully.

Once drilled, blacked-out, scrubbed, and stuffed, your tub is ready. Set it aside while you prep the substrate in Step 2.

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