The Life-Giving Roles of Moisture in the Worm Bin

The Life-Giving Roles of Moisture in the Worm Bin

For a couple of months now we’ve seen how a worm bin’s moisture level directly impacts your worms’ quality of life. We’ve learned that ultimately, somewhere between too wet and too dry is what makes a worm bin function most efficiently.

As you can see, moisture plays a huge role in the success or failure of any vermicomposting system But how exactly?

This month, we’re finished looking at the problems of inadequate moisture maintenance. We are done with our focus on the danger of parched or drowning worms. Our final installment of this series is here to wrap up the rest of what you need to know about worm composting moisture.

Today you’ll understand the ultimate benefits or roles of keeping proper moisture in your worm compost setups. You’ll learn what’s right, and how to know you’re in the zone. Not only that, we’ll share a few tips and some troubleshooting to help you keep things on track.

The Roles of Moisture in Your Worm Bin

Did you know, each year, on March 22, we celebrate World Water Day? Well, maybe we don’t all celebrate it, but it’s out there. And for good reason. We simply couldn’t live without it. Same goes for our worms.

Water plays an essential part in the worm composting process. Without it, the entire thing grinds to a halt. Why? Let’s take a look at all the ways water keeps things going.


Now there’s an important function! Without lungs like our own, a worm needs a different way to breathe. The whole length of their body comes in handy for this one. It’s right through a worm’s skin that oxygen and carbon dioxide flow.

Oxygen from the atmosphere dissolves and is absorbed through the penetrable layer of mucus that coats their skin. If this outer layer becomes dry, a worm can no longer inhale or exhale.

Appropriate moisture is a matter of life and death for compost worms!

Temperature Regulation

You may be surprised to find that water content also affects temperature regulation. A worm bin full of moist compost remains fairly consistent relative to the rise and fall in ambient air temperature.

This means that if daytime temperatures are near 75 degrees, and night temperatures fall to 50, you can expect that most of the bedding will stay closer to the average, 62.5 rather than rise and fall each day.

This offers a measure of protection when air temperatures are outside of a worm’s ideal.

Food Preparation

Remember high school Biology? Were you one of the “lucky” ones who got to dissect an earthworm? This seems like a terrible place to ask that, but it’s for a reason.

That may have been where you first learned that worms do not have teeth. Their mouth is a small muscular opening that generally allows only soft, slurpable things to pass through.

What would otherwise be inedible, is made available by the moisture in the worm bin. Water dissolves some of the food particles making them more easily consumed by the worms.

Life Force for Bacteria

As you just read, moisture helps dissolve the worms’ food. But other players in the worm bin play a more primary role in the decomposition process. Hungry bacteria feed non-stop on the same bedding and food our worms enjoy.

And what keeps bacteria living? As it is for all living things, water is the force that keeps them growing and reproducing. But don’t worry, our worms don’t have to compete for their food. Instead, quickly multiplying microbes full of nutrients become a smorgasbord for red wigglers!

As long as healthy aerobic bacteria thrive in the worm bin, there will be consistent decomposition and food available for your worms. But it should come as no surprise that without moisture, this symbiotic relationship would fall apart.

Heat Production and Rapid Decomposition

As you may have noticed, the chemical structure of food scraps and yard waste (bedding) changes as it ages in a worm bin. Yet, the rate at which this happens is dependant upon a handful of things:

  • Ingredients in the bin (carbon/nitrogen)
  • Volume of compost
  • Air temperature
  • Oxygen
  • Moisture

When all of these components work together you get decomposition. Decomposition is simply the microbial breakdown of matter. The “cool” thing about it is that the process releases energy in the form of heat.

However, without moisture, the microbes die and the process grinds to a halt.

The thing is, our worms rely on those degrees of heat, and so do we. Successfully overwintering worms depends on keeping them safely above freezing. As you’ve seen here, it may be the moisture in your bin that keeps things warm enough to keep everyone alive through the cold.

Even Distribution and Growth

Worms have amazing innate senses. They instinctively know which conditions ensure the success of a new generation. And as you could probably guess, balanced moisture is high on the list.

In a healthy, moist bin, worms are evenly distributed throughout the top layer of bedding. As they squirm about they mate regularly and deposit egg sacks multiple times per week. When laid in a well-hydrated place, the baby worms can crawl out and drink right away.

With adequate water in the bin hatchlings and juvenile worms grow quickly into mature worms.

Soon, plump worms join the mating process and continue an even life cycle.

Dilutes Acids and Bases

Eisenia fetida is a composting worm that prefers to live in neutral pH conditions. Materials given to worms with too high or low a pH can create a serious problem.

Sometimes food or bedding is introduced to the bin with a pH that is either too high or too low. Moisture in the worm bin dilutes the toxins, bringing “off” areas closer to neutral.

Nutrient Delivery

In much the same way that moisture dilutes acids and bases, moisture draws nutrients down through the bedding. Worms like to camp out right underneath their favorite foods. As they decompose, the richly saturated juices go into the bedding. There the worms slurp it right up.

Air Almost Anywhere

Deep under the compost where it’s dark, cold, and wet, worms squeeze themselves through tiny tunnels with very little space for air. However, the very humid worm bin offers worms a kind of underground life-support. 

Remember that mucus layer that covers a worm’s skin? Remember how it serves as alternative lungs? It can draw oxygen right from the water molecules in the compost! Amazing. This means worms are free to come and go, high or low, even through some water.

How to Stay on Top of Moisture Management

How often should you measure moisture? Is every day too much? What else can be done?

1. Check It

When starting out, the more often, the better. Even every day is fine. Try a probe style moisture meter for the fastest and most accurate results from the start. You can know for certain in just a moment how things are going- even well beneath the surface!

Practice: Observe, listen, and touch the bedding while you measure the moisture. Learn which readings to expect from what you see and feel.

2. Collect It

Keep your compost gathered together to conserve moisture. Worms deposit casts everywhere they go. In a worm bin that means up the sides and even under the lid sometimes. Using a scraper or spatula, it takes just a few swipes to pull together the pure red wiggler casts. Tossed back in the bedding they remain moist until harvested

3. Take The Temperature

Check both the worms’ air and bedding temperatures. Are things heating up? Are they within an acceptable range to keep your worms happy?

Temperatures in a single system may vary greatly from spot to spot depending on exposure around the outside, or from decomposition on the inside. No matter the source, as bedding temperatures rise, evaporation increases and moisture is lost to the air.

A basic probe thermometer and moisture meter are all it takes to quickly gauge how temperature may be affecting the microclimate in your bin. If it’s on the rise, evaporation is too. Be extra cautious as warming can eventually dry out worms’ bedding.

4. Strategic Feeding

Spread out servings or rotate them so that moisture is kept consistent through levels or areas of your worm bins. If you don’t care for touching the compost, a handy set of salad tongs can scoop, serve, and tuck feedings right into the ideal spots. I appreciate keeping my hands off of stinking, rotting food. How about you?

5. Make Way for Water

Keep drainage in check. Don’t allow your bedding to become too compact. Use a hand rake with blunt tines to fluff and aerate moist bedding. This allows moisture to seep through, oxygen to refresh the air pockets, and decomposition to continue. You can make it part of your feeding routine, but mostly it is something to do as a precaution or as needed.

Worm Home Solutions

When the humidity in your worm bin is just right, very little at all will stand out. Sure, you can build or buy a worm habitat that manages moisture from the start. But if you are working with a regular storage tote or outdoor pile, moisture management takes a bit of a more concerted effort.

Confident worm farmers can switch between bins, towers, or outdoor piles, but the same general guidelines apply. No matter which system of worm composting is your favorite, it’s the tools that help ensure success.

Do you occasionally wonder if your worms are dealing with too much water? An inexpensive worm composting accessory kit is the simple solution to your worms’ watery woes. With each of the five gadgets mentioned in this post, The Squirm Firm has exactly what you need to maintain a healthy environment for your worm herd.

See for yourself how much better your composting system runs when you’re equipped with the tools of your own trade! And until next time, happy worm composting!

Readers Comments (9)

  1. Another great article – very informative!!

  2. I put cover on my bins and if I close them up to much they sweat and get to moist should I put covers on or leave them off?also I have a lot of fruit flies around bin what can I do to get rid of them?

    • Hi Daniel, by all accounts it seems as if you need to let your worm bin dry out a bit. It may be that the food you add is very moist and is attracting fruit flies. If you are able to leave the lid off, or slightly off-center, the moisture can start to evaporate. As long as the worms are happy in their bedding you don’t need to worry about them escaping. Also, try tucking your food scraps under some bedding in a corner to lessen the swarming fruit flies. Even better, layer a sheet or two of newspaper over the top of your bedding. It will both absorb excess moisture and prevent fruit flies from getting to your worm’s food!

  3. I finally decided to do it right and purchased the composting bin 360 as well as the moisture and pH meters. I’d been dabbling with bins, buckets, basins and totes on and off for a few years without ever figuring out a good way to harvest the castings and separate the worms. Every time I tried there were so many baby worms left that I didn’t have the heart to leave them with the castings so I just added more bedding and more food. The population grew and declined, grew and declined depending on how much attention I paid to them. All the equipment eventually took up my entire patio.
    I’d started out with a few holy buckets in my bathroom. Then moved them into the den and now on the patio where, I fear, the cold will get them. But the totes a too big and too heavy for me to move. Should I try to harvest as many adult worms as i can from my big totes and put them into the bottom composting bin and leave the babies behind with more food and bedding in each tote?
    Or should I dump babies, eggs, casts, and compost into one huge bin add bedding and food and see how they’ll survive the winter and hope for the best. The winter’s been fairly mild here in western NC, but a hard freeze with temp in the teens is expected.

    • Dear Ines, you are a worm composting farmer at heart for sure. I was once in your predicament with maybe too many worm bins going at once. Harvesting is hard, right- so much easier just to divide the whole thing and just keep going. BUT that becomes a little too out of control. Enter the 360. I suggest you start filling up the 360 with what you have in bins. Empty out some of those bins a little at a time. Use your top tray to dry and sift as much as you can at a time and eventually you’ll get through it. The worms you harvest can go right into one of your biggest bins. In time that will become very densely populated- share or sell!

      As for the cold temps coming-if you can’t move the bins, insulate as best you can! Cover them with material that will absorb sunlight. The more bedding you have in there, the more likely the worms will survive. Even if they don’t, it is very likely that their eggs will. Come spring you’ll be right back in business! Best to you!

  4. i’ve been using the 360 system for about 6 weeks now and watching it daily. it’s hard to tell if the food is being eaten or if it’s just decomposing. also some of the veggie scraps actually seem to be sprouting! what could that mean?

    • Hi Melinda!

      Red Wiggler worms love to eat. In the right conditions, they will consume and digest 50 percent of their body weight in a 24-hour period. So if you have 1 lb of red wiggler worms, you need to put 0.5 lb of food into your worm bin.

      But if the scraps start to sprout, it means that the worms are not able to consume them as they need to and they are being overfed. Overfeeding the worms will cause issues in your worm bin such as smelly worm bin and protein poisoning. You can find helpful information about feeding your worms here:

  5. My small worm farm ( 5 layers including drain tray ) has started to become very wet. No water is collecting in the drain tray but all the vermicasts are so wet that you can ring out water from a hand full. How can I reduce the amount of moisture. I have tried adding shredded paper and straw but this has made no difference.


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