How to set up your worm composter, step by step

Getting your worm composter off to a good start gives it the best possible chance of success. Location, bedding, and patience in the first few days: here is everything you need to know for a successful start.

Choosing the right location

Temperature: a key factor

Composting worms work efficiently between 59 and 77 °F (15–25 °C). Below 59 °F (15 °C), their activity slows down. Below 41 °F (5 °C), they go dormant and stop breaking down material. Extreme temperatures — below 32 °F (0 °C) or above 113 °F (45 °C) — can be fatal to them. Your worm composter can be placed indoors (laundry room, stairwell, hallway, living room) or outdoors, depending on the space you have available. However, you may sometimes need to move it with the seasons to keep conditions right. We cover protection from cold and heat in a dedicated guide.

Weather and ventilation

If you set it up outdoors, keep it out of direct sunlight (avoid a south-facing spot). Also protect it from rain, which can get in through the ventilation holes in the lid, raise the moisture level too quickly, and drown your worms. Finally, make sure there is good air circulation in the room where it is kept: decomposition needs oxygen to work properly.

Preparing the bedding

The bedding is your worms' living space at the start — and their first source of food. It needs to stay light so that it is well aerated, while still holding the moisture the worms need to survive.

Using the bedding included with your worm composter

If your worm composter comes with coconut fiber bedding, soak it in at least half a gallon (2 liters) of lukewarm water for 15 minutes, until it breaks apart. Crumble any pieces that are still compact and mix to get an even texture that is as damp as a wrung-out sponge but not soaking wet. Pour half of it into the first tray so that the tray is half full, and set the other half aside: you will use it later as a source of carbon-rich material.

Making your own bedding

You can also make your own bedding from cardboard — for example, the box your worm composter came in. Cut it into small pieces of 0.8 to 2 in (2–5 cm) and fill half of your tray. Then spray it with water until you get the same wrung-out sponge texture.

Settling in your worms

First, place a piece of cardboard cut to the shape of the tray in the bottom of the first tray. This keeps the bedding from falling into the leachate tray. Add the damp bedding on top, filling the tray halfway, then gently pour in your worms. Leave the worm composter open, without its lid, for about ten minutes. Worms are sensitive to light, so they will naturally burrow down into the bedding.

The first week: be patient

We recommend adding a handful of coffee grounds and a few fruit peels right from the start. Worms love sugar, and coffee grounds help counteract heavily chlorinated water. Then wait about a week before adding any more food scraps, to give your worms time to get used to their new surroundings. Don't worry: they won't starve. The bedding and the material the worms were shipped in already provide them with food during this settling-in period.

Willy's tip

The most common beginner mistake is overfeeding the worm composter right from the start. Worms eat about half their body weight a day, so check whether they have finished the last food scraps you added before giving them more.

Adding your first food scraps

Once the first week has passed, you can start feeding your worms — gradually. Start with a small amount, about a handful of scraps spread over the surface of the bedding, rather than putting it all in one spot. Before each new feeding, check how the previous one is doing. If the scraps have disappeared or are well on their way, you can add a little more next time. If there is still a lot left, wait a few more days before adding more.

The worm population grows over the months, so you will be able to increase the amount of food scraps accordingly, almost naturally. It is better to slightly underfeed at the start than to overload the bin with too many fresh scraps. Excess scraps could cause the bedding to ferment and become unbalanced before the worm population has had time to catch up. It is normal for a worm composter to get going slowly: it picks up speed over several weeks, not a few days. Worms generally reach their full population after 5 to 7 months, depending on the size of your worm composter.

The role of the moisture mat

The moisture mat sits under the lid, directly on top of the freshest scraps, and serves two practical purposes. First, it keeps the surface moist while letting air circulate — giving the worms the feeling of being just below the soil surface, as in nature. Second, it limits fruit flies' access to the fresh scraps. There is no need to dampen it at the start: it naturally absorbs moisture from contact with the scraps.

Which material should you choose?

Several materials work well. Plain brown cardboard is free and easy to cut to the size of the tray, but it needs replacing often. Hemp fiber, often included with store-bought worm composters, should be changed every two to three months. Burlap lasts longer. You can also use an old cotton fabric (a rag, a T-shirt), as long as it contains no detergent or synthetic products. Once the mat has broken down well, you can crumble it and mix it into the scraps, where it will act as a source of carbon-rich material.

Did you know?

A moisture mat is really just a miniature layer of forest-floor litter: it makes the worms believe they are still just below the surface, where they feel most at home.

What's next?

Your worm composter is ready to get going. To find out exactly what to feed it — and what is best avoided — head to our guide What do earthworms eat?. If you don't have your worms yet, first read our guide Which type of worms should you use in your worm composter?

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