Worm Bin Temperature
Ideal Worm Composting Temperatures
For most composting with Red Wigglers, the ideal temperature is 77 degrees Fahrenheit, or 25 degrees Celsius. This is the most efficient temperature for food consumption rate as well as reproduction rates.
Red Wigglers will still do well around 60-80 degrees, but their efficiency will diminish beyond that range, and risk dying above 90F and below 32F.
It is better to be too cold than too hot.
See the chart below for an illustrative representation of temperatures effect on red wiggler's efficiency.
You can use a thermometer to check the temperature of the bin, but I think most people will be able to tell just by touch so I don't really push buying a thermometer for this.
Factors that Affect Temperature to Consider
Ambient Temperature
The temperature inside the bin is what matters most, but the outside temperature is the main consideration in keeping the worm bin temperature ideal. If possible, keep the worms indoors where the temperature will remain between 60-80°F
Sunlight or Shade
Strategically placing your worm bin in either the sun, or in shade, can help keep the worm bin cool or warm respectively.
If you are placing the worm bin in the sun, pay extra attention to the internal temperatures. The sun can warm up a worm bin quicker and higher than you might guess.
Insulation of the Bin
The better insulated the worm bin is, the less it is affected by exterior temperatures. Straw is a cheap and easy worm bin insulation to use in outdoor systems.
Size of the Worm Bin - Thermal Mass
Larger worm bins/compost piles hold their temperatures better - tending to have a higher temperature.
Internal Heat from Microbial Growth
As microorganisms reproduce, they generate heat. When you have many microorganisms, like in a worm bin, they will generate noticeable heat. Your worm bin will almost always be slightly warmer than ambient temperature due to this.
Take care to not add too much nutrition at once as it can cause a rapid spike in bacterial growth, which can cause a worm bin to heat up well over what they can handle.
Moisture Levels
Water transfers heat/cold very efficiently. The more moisture in a worm bin, the more temperature can be transferred into it. Drier bins are less affected by extreme temperatures than wet bins.
Submerging the Bin
I'm not a big fan of submerged worm bins, but just as another idea; you can partially bury a worm bin to take advantage of the more stable temperatures.
How to Manage Worm Bin Temperature
How to Keep a Worm Farm Warm
- Keep the Worm Bin in your home or garage if possible
- If outdoors, place it in the sun.
- Insulate the bin by placing thick layers of straw, or other insulation, around it.
- Increase the size of the worm bin.
- Add higher amounts of nitrogen rich feeds. Proceed with caution.
- Run the worm bin on the drier side.
- Add heat packs, or warm waterbottles, into the bin.
- Use a seed-heating mat under your worm bin if possible.
How to Keep a Worm Farm Cool
- Keep the Worm Bin in your home or garage if possible.
- If outdoors, place it in the shade.
- Insulate the bin by placing thick layers of straw, or other insulation, around it.
- Decrease the size of the worm bin. Don't go smaller than a few gallons.
- Add less high nitrogen foods, and/or add them in smaller amounts more frequently.
- Run the bin on the drier side.
- Add frozen ice packs, such as ice cubes in a plastic baggy, into the bin.
Scott Kent
Owner of Hungry Worms. Worm farmer, soil microbiologist, and educator since 2014. Read more about me here.