How to maintain correct moisture levels in your Worm Bin

Worms in your worm bin need moisture to survive. Their skin needs to be moist, or else they can’t breathe. Often we add too much or too less water in the worm bin and end up with undesired results. When I started, I faced the same problem, but now after doing it for a while, I know everything there is to know about maintaining a healthy worm bin. I am really excited to share my experience with you. Let’s start with a common question.

How often to water the worm bin? Most worm bins rarely require the addition of additional water. In most cases, the moisture content in the raw materials furnishes the required water. Ideally, the compost should have a wet sponge consistency. If it feels dry, you should spray small amounts of water on the top.

This is just a generalist view, though. There is so much more about maintaining the correct moisture levels in your worm bin. Let’s dive a little deeper into it.

How much moisture do you need in your worm bin?

Most studies recommend 75%-80% moisture in a worm bin, though it can vary slightly based on the raw materials you are using. A time tested way is to check the consistency of the compost regularly. It should feel like a wet sponge (Its a little less scientific, but it works!)

Types of Compost Bins

The compost setup that you are using can also affect the moisture levels in a pile.

  • Plastic Bins – If you have a plastic bin, you rarely need to add additional water. In fact, it’s mostly the other way around. Most plastic-based compost bins retain water well (Sometimes too well!)
  • Wood-Based Composting Systems: If you have your composting pile in a wooden container, you may have to spray some water once in a while.
  • Open Pits: Open pits may require regular addition of water. You need to check the top surface of the pile often. If it feels dry, spray a small quantity of water on it.

Worm Bin Is Too Wet

It is pretty standard that despite all our efforts, we end up with a composting bin that is too wet.

What happens if it is too wet

  • Reduces Oxygen Supply – Too much water can hamper the airflow, making it harder for the worms to breathe.
  • Anaerobic Pit: In the absence of oxygen, the microbes in a pile start anaerobic processes, which produces ammonia gas, And we all know how it smells!
  • Lower Productivity: If the bin is too wet, worms start looking for drier places and may also turn pale. This reduces the speed of composting, making you wait longer for the output.
  • White Maggots: A wetter bin also invites black soldier fly to lay eggs in a pile. These eggs develop into larvae, which a lot of people don’t like.
  • Fungal Growth: A wet pile may have a higher acidity, which results in fungal growth.


  • Drainage Problems: It’s common for the drainage holes to get blocked with worm castings. This can restrict the outward flow of water, causing water accumulation in the bin.
  • You are adding a lot of water – This is pretty obvious, but I would still like to point it out. Sometimes we incorrectly assume that the pile is dry and keep adding water to it. This water eventually clogs up the bin.
  • Materials with high water content: This is one of the most common reasons associated with a wet bin. Fruits and vegetables can be 80-90% per cent water. This can quickly add up without you even realising it.
  • Bedding Issues: Bedding absorbs the excess water in the bin, hence balancing the moisture levels. If you are not adding the bedding properly or not using it, it can cause a wet pile.
  • Rainfall: If your bin is in the open, and it rains, the water will enter the container. If it rains often, the bin will have more than it can handle


  • An excellent way to reduce excess moisture is to add some fresh bedding to the pile. You can add some paper bits, straw, cardboard pieces or sawdust.
  • If you have some drainage holes, you can tilt the bucket so excess water can flow out out the holes. You should also check the spots for blockage. And remember to keep the bin on a plastic container, so drainage doesn’t create a mess.
  • Stop adding materials with high moisture content in the bin until optimal consistency is attained.

Worm Bin Is too Dry

Like a vermicomposting bin that is too wet, an overly dry bin is wrong for the composting process as well.

What happens if it is too dry

  • Microorganisms Perish – Microorganisms, like most living things, need water to live. In a dry composting pile, they dehydrate and die. Without these beneficial microorganisms, there is no composting.
  • Worms Suffocate – If you look closely in a vermicomposting pile, you can see that they live closer to the moist parts. The moisture helps them retain the slippery layer of mucus on their skin. This layer is required for breathing. They take in oxygen and release carbon dioxide from their skin. When the bin is too dry, they start losing their mucus layer, making it impossible for them to breathe. Eventually, they start dying of asphyxiation.
  • Worms Gather at one place – Worms are a cooperative species. When the moisture is low, they assemble at one part to live off the remaining bits of water.
  • Worms May Leave The Pile – If the conditions in a pile are inhospitable, the worms start leaving the stack to search out more welcoming places.


  • Adding Too Many Dry Components: Things like cardboard, paper etc., soak up the water. These should be added in accordance with moisture levels. If you keep adding them, they will ultimately dry up the pile.
  • Hot Weather: If you live somewhere hot, the water in your pile can evaporate. Keeping the composting bin in direct sunlight can also cause dryness.


  • Spray Water: To add moisture to the pile, start by spraying the surface with water. Add small quantities in the beginning and check the moisture levels regularly.
  • Add More Greens: A better and long-term solution is to add more green materials like fruit, vegetables, and peels into the composting bin. These are high in water content and add moisture more naturally.

How to check moisture content in a worm bin

Gauging the moisture levels in your bin is crucial to determine if it is too dry, too wet or normal. Let’s talk about various ways of measuring moisture in a vermicompost bin.

  • Squeeze Test: Take a handful of compost and squeeze it. If there are more that one or two drops of water coming out, it is too wet. One the other hand, if it feels sandy, coarse or crumbles in your hands, it is too dry. Ideally, it should feel like a wet sponge.
  • Worm Compost Moisture Meter: If you want something precise, this is the way to go. A moisture meter can accurately gauge moisture levels in your compost pile and alert you if it is too dry or too wet. It is especially helpful in accessing the situation during changing seasons. You should insert it at different sections of the pile to get a bigger picture. It is pretty common to have pockets of the dry and wet mixture in the same stack, especially if you are not mixing it regularly.

Materials with high moisture content

It’s good to have an idea of moisture content in some materials that we often add to the composting piles

Vegetables with high moisture content (80% to 95%)
Green Cabbage
Iceberg Lettuce
Fruits With high moisture content (80% to 95%)

Final Thoughts

Maintaining the correct moisture levels is one of the most crucial elements of composting or vermicomposting. Initially, it may be a little difficult to judge the water levels in the bin, but after a few batches, you can quickly tell if it is too dry or too wet. Just don’t over-stress it, and remember to have fun in the process!


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