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Why Are My Compost Worms Dying? 6 Common Causes & Solutions

Why Are My Compost Worms Dying? 6 Common Causes & Solutions

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Paul Brown

When you start to see dead worms in your bin, it can be concerning. Worms have a natural lifecycle like all living things but if there is a sudden increase in the number of worms dying, it is important to identify the cause. In most cases, it is a simple matter of identifying the reason and correcting it.

Reasons that compost worms may begin dying include:

  • Lack of oxygen
  • Poor moisture conditions
  • Temperature extremes
  • Toxic bedding materials
  • Poor quality of food and water
  • Protein Poisoning

These issues can lead to sickness, disease, and eventually death of compost worms.

Let’s get a little background and clarity on each of these so that you will know what to watch for, prevent, and how to correct these issues if you have them.

Worms Dying From Lack Of Oxygen

Worms breathe through their skin but they do require oxygen. One issue that I’ve seen causing a lack of oxygen in a worm bin is not having enough air holes. It’s a simple fix but it’s critical that sufficient fresh air is allowed to ventilate through the bin. And air holes serve more purposes than just fresh air so make sure that you have enough of them.

If you are concerned that your worms will crawl out through the air holes, read this to learn why worms try to escape.

Poor Moisture Conditions

Of all of the troubleshooting topics that I’ve covered, inappropriate moisture conditions is the most common by far. This is because it seems to be the easiest to mess up. Issues can arise when the bedding is too wet or too dry, so let’s address each of them separately:

Too Much Moisture

Knowing that worms require a moist environment, people often overdue this. What is important to remember is that in addition to water you add to the bin for moisture, a lot of the foods that worms eat are also water-rich. Fruits and vegetables, for example, often have high water content.

Another issue may be that the bin is not draining effectively. If you are not seeing liquid seeping from the drain holes in the bottom of the bin, make sure that the holes are not clogged. This can result in pooling of water at the bottom of the bin. Click Here to read about the reasons why your bin might not be producing liquid.

Moisture is important but you don’t want the bedding to be saturated.

Learn more about wet bin problems.

Not Enough Moisture

At the other end of the spectrum is an environment that doesn’t have enough moisture. Worms are mostly water content by weight and they need a steady supply of moisture in their environment to survive.

If your bedding is dry, spray water into it and mix the bedding a little to make sure there is sufficient moisture throughout. Increase water-rich foods for a few days. It’s a simple fix but overlooking this can have deadly results for your red wigglers.

Note: This can feel a little confusing – “Is my bin too wet or not wet enough?” but as a rule, it’s better for it to be a little too wet rather than too dry (source). The real key here is to monitor the moisture and make sure that the bin doesn’t get way out of balance.

Temperature Extremes Can Cause Worms To Die

Worms can die if they are exposed to extreme temperatures (source). Their bodies are not designed to withstand extremely cold or hot climates. They do best in very moderate conditions which is one of the reasons vermicomposting is a favorite solution for indoor composting. But you don’t have to keep them in your kitchen. An attached garage or even an insulated shed should provide protection from very cold temperatures.

In the summer, it’s important to keep your bin in a shaded area and to keep an eye on the moisture levels. Pouring some ice on the top of the bedding is a great solution because it dissolves and absorbs slowly while cooling the bedding. The worms will move away from the extreme cold but they’ll slowly move back up as the temperature equalizes.

Toxic Bedding Materials That Can Kill Worms

Your worms will feed on their bedding so it’s important to be mindful of the quality of materials that you are using. Most of these issues come from a misunderstanding of best practices. For example,

  • Shredded paper is often recommended but if you are using the glossy advertising mailers that we all receive in our mailbox all too often, those contain chemicals that can throw your bin out of balance.
  • Shredded Cardboard is an excellent bedding material but not the glossy colored types like cereal boxes.

The best approach to avoid toxic bedding situations is to just use common sense. Try to stay as organic and pure as you can with the materials that you use. Amazon boxes can be used and so can most paper towels.

A great solution is those brown recycled paper towels (link to Amazon) that are often used in restaurants and convenience store restrooms. I keep some of these in my garage for cleaning purposes but there’s no need to buy any unless you have a use for them. Just avoid overly chemically-treated materials.

Poor Quality Food Or Water

What you put in, you get out. It’s true in almost everything in life and it’s no different with vermicomposting. Worms can eat slightly molded or rotted food in smaller quantities, for example, but that shouldn’t be their entire diet. A steady supply of fresh food scraps is best. Don’t overfeed or you will end up with uneaten food and the bin will begin to smell.

If you notice that they aren’t feeding, the quality of food may be the reason. Click here to learn more reasons that your worms may not be eating.

Water is another consideration. I will tell you that I’ve decided that rainwater is by far the best solution. It’s free of chemicals and you don’t have to worry about hard water, chlorination, or other potential issues. I’ve studied a lot of literature and there is some debate on whether or not chlorinated water is a significant concern but to be safe dechlorinated is probably a better solution if you don’t have a way to harvest rainwater.

Protein Poisoning

Also known as Sour Crop or String of Pearls, protein poisoning, is a sickness that can occur due to a buildup of protein in compost worms. When this occurs, the body of the worm can begin to look as if there are missing sections which is why it is often referred to as string of pearls. The most common cause of this is overfeeding that allows proteins to accumulate in the bedding (source).

You should remove worms that are showing signs of protein poisoning. Next, you’ll want to take account of what food items you have been putting into your bin. I suggest removing any uneaten food scraps at this point and essentially starting over. Sour Crop isn’t contagious to other worms but the environment is clearly out of balance and if not corrected other worms will show similar symptoms. You may need to hold off on feeding the worms for a few days while you get the bin back into balance.

What About Diseases Causing Worms to Die?

It’s actually very unusual for red wigglers to have issues with diseases, in part because of the environment that they create. In the process of consuming food and depositing castings, the bedding becomes very oxygenated. This creates a hostile environment for many disease-causing bacteria that require anaerobic conditions. In addition, as food is passed through the body of the worm, its own internal system is unfriendly to bad bacteria, further reducing the likelihood of diseases (source).

Where problems can occur is when we disturb the natural aerobic conditions by either adding so much moisture that the bedding packs tightly preventing air or when we don’t ensure that there are enough air holes to allow for adequate ventilation.


If you provide an environment for your red wigglers that meets their needs, they should live for several years and die out slowly as part of the natural process of life. If your worms are dying in clusters, make sure that you take the time to troubleshoot the conditions of your bin using these suggestions. If you identify the problem and correct it, the population of your bin will normalize over time.

Be sure to read our complete guide to Keeping Compost Worms Healthy And Happy