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Can Composting Worms Drown? Wet Bin Vermicomposting Problems

Can Composting Worms Drown? Wet Bin Vermicomposting Problems

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Paul Brown

Worm composting (also called vermicomposting), using worms to recycle food scraps and other organic material, is becoming a popular method to add valuable and highly fertile soil back to gardens and other projects. It’s a simple and easy solution for composting that can be done indoors while making use of food scraps such as fruits and vegetables. Moisture content is important too but how much water is okay? I researched this because I wondered if I could overdo it and harm the worms?

Can composting worms drown?  Yes, composting worms can drown. Since worms breathe through their skin, they can drown in a composting container in at least three ways:

  • The worm bin is watered too often
  • There is not enough drainage to carry away excess moisture
  • The worms manage to fall or dig down into liquids pooled at the bottom

Note that worms can actually live up to two weeks underwater but this is dependant on the water having ample amounts of oxygen. Vermiponics systems infuse oxygen into the water which prevents worms from drowning. So, it could be said that rather than drowning, the worms actually suffocate underwater when there is not enough oxygen to keep them alive.

This article will focus on the three ways worms can drown in a vermicompost bin and how to make sure that it doesn’t happen in your worm bin.

The Worm Bin is Watered Too Often

Moisture is vital to helping the worms in the bin consume the scraps and to help keep the worms themselves from drying out. Adding water to the bin is something that needs to be done after careful monitoring to make sure that the mixture inside is nice and moist but not pooling at the bottom.

By maintaining moist compost bedding without forming puddles of liquid, you can provide the needed moisture without risk of your worms drowning (Source: The Environmental Protection Agency).

There are moisture level monitors that you can buy for this (link to Amazon) but the simplest way to monitor moisture is to feel around in the bed for excess water. It usually collects at the bottom of the bin so you may need to move a little bedding to check. What you are looking for is the pooling of fluids. If you see any, it needs to be corrected (keep reading for solutions).

Maintaining Drainage

Worms love moisture, and it is typically recommended to keep a composting bin at the 60-70% moisture content level. While the percentage of moisture is vital, so is controlling the runoff that will accumulate at the bottom of the compost bin.

If too much liquid is produced by the worms or put in by the harvester, the worms cannot breathe and will become sick or drown.

The best way to alleviate this problem is to make sure there are adequate holes in the bottom of the bin to allow the liquid to drain out or to install a drainage system at the bottom of the bin. This can include a spigot to allow the draining of excess fluids.

Preventing Puddling at the Bottom

Puddling of fluids at the bottom of the bin should be avoided so that worms aren’t at risk of falling into any pools in the bin and drowning. This is especially true if the worms feel the need to dig deeper to find nutrients because the bin has not been fed adequately.

By making certain the worms are happy at the upper levels of the bin by maintaining the correct moisture level and feeding them adequate foods, the worms will not dig down deep and face the possibility of drowning. Also, remember that many fruits and vegetable scraps that are added to a worm bin are often very moisture-rich. The high level of water content in these foods will add to the total moisture content within the bin.

What To Do If Vermicompost is Too Wet?

While worms can drown in vermicompost that is too wet, there are five methods one can take to solve the problem including:

  • Cleaning up visible puddles
  • Adding moist scraps in moderation
  • Adding more bedding (shredded paper and cardboard)
  • Removing the lid and using a fan
  • Shining a warm light on the bin

Each method is described in better detail below.

Cleaning up visible puddles involves using paper towels or rags to sop up excess fluid that has accumulated on top of the compost. This will prevent the extra fluid from draining down into the bin, where it can cause worms to drown.

Not adding moist scraps of food to the vermicompost bin will limit how much fluid can accumulate in the bottom. Feeding drier scraps such as carrots and other foods lower in moisture instead of melons or other fruits will be helpful in eliminating moisture build-up.

But remember that the worms do need moisture and water-rich foods are excellent for worms so moderation is key. You don’t want to eliminate these foods but if you notice the bin getting a little too wet, ease off of foods with high moisture content for a day or two.

Adding more bedding is enormously helpful because the bedding is made up of scraps of cardboard, paper, and newspaper that are highly absorbent and will wick away excess moisture.

Removing the lid and using a fan will assist any excess moisture to evaporate alleviating the chances the worms will drown. However, this method should be used only for short bursts of time since one does not want the bin drying out. Careful monitoring is necessary to ensure the worms remain healthy and active.

Shining a Warm Light on the Bin will assist the drying process while driving the worms away from the heat of the lamp. However, like with using the fan, careful monitoring is necessary. You do not want the bin to get too warm, and worms do not like bright light, so they may dig deeper and end up drowning in any fluid collected at the bottom of the bin.

I’m personally not in favor of this approach because it puts the worms at risk if you don’t closely monitor them. I’m including it only because it is an option but I recommend first working to get the excess water out through the other methods.

Why Do Vermicomposting Bins Get Too Wet?

While moisture is a necessary component for worms to do their work converting table scraps into well-fertilized soil, too much wetness can cause diseases and drown worms.

Vermicomposting success really comes down to maintaining a healthy balance. Choosing the right foods and moderating the amount of water you add are important aspects of maintaining proper moisture levels. But if you are seeing excess moisture in your bin, there are two important questions you need to ask yourself:

  • Is the bin in a high moisture location?
  • Are there enough drainage holes in the bottom?

Let’s take a look at each of these problems and some simple answers.

Is The Worm Bin In A High Moisture Location?

Leaving a vermicompost bin in the open outside where rain can get in or where there is too much humidity indoors next to a pool or on an uncovered back porch can be the source of excess moisture. The solution is simple; move the worm bin to a less humid location such as under a covered patio, porch, or to a room without high moisture levels.

I originally thought our pantry would make an excellent location for my vermicompost bin but my wife adamantly disagreed. 🙂

Closets are favorites among many vermicomposters who prefer to keep their worms indoors because the rooms can be kept dark. A garage or shed can work as well, just be mindful that uninsulated areas are still prone to weather extremes.

Are There Enough Drainage Holes in the Bottom?

Store-bought vermicompost bins like this one (link to Amazon) are designed with enough holes drilled into the bottom of the bin and often a spigot to help excess moisture escape. But, homemade compost bins may not adequately have enough holes to allow excess moisture to drain away.

The simple fix is to add more holes but to be careful not to make them so big as to invite worms falling through them. A series of smaller holes is much more effective than a few large ones in this case, so drill away. Also, be sure to check them anytime you notice that your bin is not producing any liquid in the reservoir. This could be a sign of the holes being clogged.

Placing a Worm Bin Blanket on Top of the Bedding

To prevent a compost bin from becoming too moist or drying out when stored outdoors, one option is to utilize a worm bin blanket. A worm bin blanket will protect the worms from rain (and thus drowning), light, and hold in the heat in colder climates.

When monitored closely, a warm blanket on top of the compost will keep it from getting too wet and not too dry. At the same time, it does have the benefit (and risk) of holding in moisture so those drainage holes I mentioned earlier are still important.

You can purchase a worm blanket online (link to Amazon) or even use an old piece of carpeting but there are two distinct types of worm bin blankets, with each having its purpose depending on whether it is to be used outdoors or indoors.

  • Indoor blankets like the one I linked to on Amazon offer protection from moisture building up in the bin when it’s kept inside a home.
  • Outdoor blankets keep the rain away that can quickly stink up a compost bin and drown the worms. Personally, for an outdoor bin, I would prefer to use a solid cover with some holes in it. This has the added benefit of keeping pests such as rodents out of the bin if you can cover it completely.

Manufactured Versus Homemade Vermicompost Bins

I love DIY projects so building a vermicomposting bin was a fun and creative adventure for me. Not everyone wants to go the Do-It-Yourself route though and I can appreciate that. The truth is, there are some distinct advantages that a manufactured worm bin has over my DIY solution.

First, these bins are produced with moisture control in mind. They are designed to alleviate drainage issues from the start. And so, there is no trial and error involved in drilling holes and wondering if you have enough. Second, the spigot that many of them include allowing for fluid to pool into a secondary container and then be drained into a cup or bowl to be used as a liquid fertilizer that is bursting with nutrients. And I appreciate the no-waste concept.

But homemade vermicompost bins are highly effective when the proper precautions are taken to allow for adequate drainage so that the worms will not drown. By adding enough drainage holes designing a system that still collects the excess moisture, you can solve the problem of worms drowning and use the fertilized liquid just like manufactured bins do.

A common solution is to place one container into another, creating an airspace at the bottom where fluid can collect. You drill holes in the top container but not the bottom one. Excess moisture drains out of the top container (where the worms are) and collects in the bottom container. This video on Youtube demonstrates the concept. Although the host actually uses three containers, the concept is the same. He even adds a spigot to the side.

Building a Stackable DIY Worm Farm for $30 🐛

It’s worth noting that I often see people demonstrating drilling holes in DIY worm bins using a 1/4 inch drill bit. I chose to use a 1/8 inch bit. These holes are much smaller to help prevent worms from falling through to the bottom tray where they could drown. Since they don’t drain as quickly as larger holes would, I simply drilled more holes.


Worms can drown in vermicompost bins that do not have their moisture content well regulated. Preventing this is a simple matter of adding adequate but not excessive water, maintaining an effective draining system, and designing your bin so that worms are not falling into pockets of pooled water.

With just a little effort, you can establish a bin where red wiggler compost worms are happy and content with enough moisture to keep them healthy but not so much that they are at risk of drowning.

Click Here to learn why Vermicompost is better than manure as a fertilizer for your garden and flowers.