All-in-One Grow Bag Troubleshooting Guide | Fix Common Issues

Growing mushrooms with an all-in-one grow bag is one of the easiest ways to get started in mycology, but like any grow, things don’t always go perfectly. Whether you’re dealing with stalled colonization, strange-looking mushrooms, or moisture problems, this guide will help you identify common issues and how to fix them.

Understanding the All-in-One Grow Bag Process

Before troubleshooting, let’s quickly go over how an all-in-one bag works:

•  The bag contains both sterilized grain (which gets colonized first) and bulk substrate (where the mushrooms will actually grow).

• After inoculation, the mycelium colonizes the grain before spreading into the bulk substrate.

•  Once fully colonized, fresh air exchange (FAE) is introduced to trigger fruiting.

•  Mushrooms grow, are harvested, and in many cases, a second flush follows.

Now, let’s break down common issues and how to fix them.

Troubleshooting Guide

1. Mushrooms Only Growing in Small Clusters

Problem: Instead of a full flush, only small clusters of mushrooms are growing in random spots.

Cause: This usually means there’s not enough fresh air exchange (FAE). In an all-in-one bag, mushrooms tend to form near the filter patch or anywhere they can get oxygen.

Solution:

✅ Once fully colonized, cut open the top of the bag or poke small holes in it to allow for more air circulation.

✅ Keep humidity high after opening by misting as needed.

✅ If using a fruiting chamber or humidity tent, increase airflow without drying out the mushrooms.

2. Mushrooms Appear Grayish or Off-Color

Problem: Mushrooms or parts of the substrate look gray, fuzzy, or discolored.

Cause: This could be cobweb mold, which thrives in still, humid environments and can smother mycelium.

Solution:

✅ Lightly mist affected areas with 3% hydrogen peroxide to kill cobweb mold.

✅ Increase fresh air exchange by opening the bag more or fanning lightly.

✅ If discoloration is bluish and doesn’t wipe off, it’s probably bruising from dryness—lightly mist with water instead.

3. Colonization Stalled or Taking Too Long

Problem: The mycelium isn’t spreading, or growth has completely stopped.

Cause: Could be low temperatures, too much moisture, or bacterial contamination.

Solution:

✅ Keep colonization temperatures between 70-75°F. If it’s too cold, move the bag somewhere warmer.

✅ If the grain is partially colonized, gently break it up and mix it into the substrate to speed up colonization.

✅ If there’s a sour smell or slime, bacteria may have taken over—toss the bag and try again with better sterile technique.

4. Too Much Moisture or Condensation in the Bag

Problem: Water is pooling inside the bag, or the substrate looks overly wet.

Cause: Temperature swings and lack of airflow can cause condensation buildup, leading to excess moisture.

Solution:

✅ If condensation is light, leave it alone—it’s normal.

✅ If there’s pooling water, loosen the bag slightly or poke a small vent hole to release humidity.

✅ Tilt the bag gently to drain excess water if needed.

5. Substrate Looks Too Dry

Problem: The substrate appears dry or shrunk, and there’s little to no condensation in the bag.

Cause: Lack of moisture or too much fresh air escaping during colonization.

Solution:

✅ Make sure the bag is sealed properly during colonization to keep humidity in.

✅ If the substrate is visibly dry, mist inside the bag lightly with clean water.

✅ In extreme cases, inject a small amount of sterile water through the injection port to rehydrate.

6. Uneven Growth or Only One Side Colonizing

Problem: One side of the bag is colonizing much faster than the other.

Cause: Uneven spore distribution or lack of airflow to certain parts of the bag.

Solution:

✅ When inoculating, inject spores or liquid culture in multiple spots instead of one area.

✅ At 30-50% colonization, mix the grain inside the bag to evenly distribute mycelium.

✅ Rotate the bag occasionally to ensure all sides receive equal airflow and light.

7. Mushrooms Growing Tall and Skinny (Leggy Growth)

Problem: Mushrooms are thin with long stems and small caps.

Cause: Not enough fresh air exchange (FAE), leading to high CO₂ levels.

Solution:

✅ Open the bag more to allow for better airflow.

✅ If using a humidity tent, add extra ventilation holes.

✅ Lightly fan the bag a couple of times per day to help balance CO₂ levels.

Final Tips & When to Start Over

If your bag is contaminated (green, black, or pink mold, strong sour smell), there’s no saving it—toss it and start fresh. Learning proper sterile techniques and understanding environmental control will help you improve each grow.