Vermicomposting: Troubleshooting

A worm bin acts much like a small ecosystem, with several processes all influencing each other. If one of these processes goes wrong or one of the inputs is off, the whole system can be thrown off balance. Below are some of the common issues you are most likely to encounter, and some possible solutions:

Bad Odor

Odors can have several causes, including food rotting before worms have a chance to eat it and too much moisture or too little ventilation preventing proper oxygen flow. If food is rotting, you most likely have too much nitrogen relative to carbon and will soon start producing ammonia, which can kill your worms. Remove excess food and add additional bedding material. If the odor is from a lack of oxygen flow, leave your bin open to air out when you can supervise it and mix up all material with your hand to improve air circulation to lower levels. See “water not draining/bin too wet” below for additional help.


Flies are attracted to food waste and just a few can lay eggs and cause a huge infestation. To prevent flies, keep food covered with a layer of dry bedding such as shredded newspaper. Because the types of flies that tend to inhabit worm bins cannot burrow, covering food blocks their access and their ability to breed.

Water Not Draining/Too Wet

Worm bins must have adequate drainage. Ensure that drainage holes are not clogged by wiping a paper towel over the bottom of the bin. Absorb excess water by adding additional dry, absorbent bedding such as shredded newspaper to the top of the bin– even if it is not mixed in to the wet layers, the humidity in the overall system will balance over the next few days and the paper will soak up some of the excess. If you have pools of water, you can remove them with minimal disturbance to your bin by rolling a paper towel into a tube and placing one end in the pool and the other end pointed upward and reaching past the surface of whatever material you have in the bin. The paper towel will wick up the excess moisture, simply remove it once the puddle has vanished.

Keep in mind that plastic bins tend to hold excess moisture, while wood bins are more likely to dry out. You may want to slightly adjust your bin maintenance depending on your bin type.

Worms Wandering/Leaving Bin

Worms are generally fairly tolerant, but if a system gets out of whack they will attempt to escape the problem by leaving the bin. This is most often caused by anaerobic conditions or ammonia production brought on by overfeeding, and less often but sometimes due to hot temperatures. Remove excess food, mix material lightly to improve oxygen flow, and make sure the bin is kept out of the sun and at room temperature.

If everything seems fine and the worms have been happy for months but suddenly start trying to escape or dying off, it is probably time to harvest finished castings from the bin. Worms can live in compost for quite a while but it is still their own waste product, and they will eventually (and seemingly suddenly) hit a point where they’ve had enough. See our harvesting page for help on harvesting finished castings.

Bin Drying Out Quickly

If your bin is too dry, the easiest solution is simply to regularly add water with a watering can. You will want to add small quantities of water often rather than large quantities rarely in order to avoid pooling. Dry bins are completely inhospitable to worms, who require plenty of moisture to keep their skin healthy. If your bin is drying too quickly, consider using a wetter food source or covering the material with a breathable fabric like burlap– just don’t reduce air flow!

This is, of course, a fairly simple guide for a complex ecosystem. If you are having other troubles or have questions, please feel free to contact us!

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