Mixing Substrate & Spawn for Mono-Tubs

A tutorial on how to mix substrate & spawn for "MonoTubs"


It's crucial to read through all directions thoroughly and ensure that you have a complete understanding of the process before beginning. This will help you avoid potential mistakes or complications that could lead to sub-optimal results. Take your time, carefully review all the instructions, and don't hesitate to seek clarification if anything is unclear. By doing so you'll set yourself up for a successful and rewarding experience.

Finding a clean place to work is essential to prevent contamination. A flowhood is a specialized piece of equipment and should be used. But if a flowhood is not available, a clean, draft-less room can a good alternative.

Before You Start

Gather the materials you'll need:

  • fully colonized grain spawn
  • sterilized substrate
  • tote/tub, with good a fitting lid
  • 70% isopropyl alcohol (iso)
  • paper towels


  • gloves
  • garbage bag or similar (for liner)
  • scissors for liner

Determine amount of substrate and grain spawn needed.

We recommend using a 1:2 ratio,
which means using one 4lb (2.5qt) bag of our grain spawn per one 8lb (5qt) bag of our substrate. For optimal results, aim for a depth of 2-5 inches when mixing the ingredients in your totes. Use the photo below with your measurements in inches to determine how many liters you need with "H" being the depth of substrate you choose.

Step #1

Put on gloves if using them and then wipe your hands/gloves down with an iso soaked paper towel, being sure to scrub them thoroughly. Wet a new paper towel with iso and use it to clean the inside of your tote and its lid thoroughly.

Step #2

While still in the bag start by carefully breaking up the colonized
grain spawn into smaller pieces. Take care not to damage the bags or
puncture the filter. Ensure that all the grain is separated and no large chunks remain.

Step #3

Wipe down your bags of spawn and substrate. It's crucial that your tub, hands, spawn and sub bags are completely clean before adding any of the ingredients and mixing.

Step #4

Cut open your substrate bag and empty it into the tote. Break up any large chunks. Cut open and add your grain spawn to the tote.

Step #5

Mix the spawn and substrate thoroughly being sure not to leave any unmixed patches in corners, bottom or sides. It is very important no large chunks of only substrate or gain remain.

Step #6

Even off the top of your mix by shaking the tote back and forth, do not pack it. You want it to remain fluffy but remove any air pockets and get the surface as even as you can.


Put the lid on and wait! Cover around the lid with plastic wrap if it makes a poor seal to keep the humidity high, but you most likely don't have too. To ensure proper growth, keep the tote/tub between 65-85°F. Avoid exceeding 90°F, disturbing the tote and any bright/harsh light. It can take anywhere from less than a week to 3 for the tote to fully colonize depending on temperature, ratios and size. You will know it is ready, following a few days after the entire top surface is white. Once it looks fully colonized or small pins start to develop follow along with our steps in "Fruiting a Mono-Tub" for more help!