Compost worms

Source: crabchick

Compost worms

Composting in a wormery is the best solution when living in an apartment.

It allows you to recycle vegetable kitchen waste into compost and percolate.

A wormery requires more attention than composting in the garden, especially when starting a new wormery.

If you do not spend time to check the wormery regularly, the balance may be disturbed and the wormery will stink.

So there is a learning curve during which you will need to observe how much waste your worms can digest.

Advantages of composting in a wormery:

  • You reduce your amount of waste and save on garbage bags.
  • You harvest compost and percolate which can be used as organic fertilizer for your patio and houseplants.
  • Fishermen can use the worms as bait.
  • The worms can be used as food for terrarium animals.

What do you harvest:


Compost is digested organic material that can be mixed with potting soil.

It is rich in nutrients and a good fertilizer for your plants.

The compost is harvested 1 to 2 times a year.


Percolate is the liquid that drips into the lowest box.

It can be used diluted as fertilizer when watering your patio and houseplants.

Percolate can be drained approximately weekly.


Source: Mike


Wormery models:

There are 3 models:

Horizontal wormery:

This is rarely used because it takes too much space and is therefore less suitable for use in an apartment.


A monobox is a high box with a lid and at the bottom a perforated double bottom and tap.

This model has the advantage that you can throw waste on continuously on top but as a disadvantage, it is difficult to check if the wormery is healthy and you have to remove everything to harvest the ripe compost that is underneath.

Another drawback is that the tap can leak.

Stackable box wormery:

This consists of 3 or stackable boxes (Curver or Alibert type).

The lower non-perforated box is the receptacle for the percolate. You can install a tap, but then you risk leakage.

The upper 2 (3) are perforated at the bottom to allow the worms to migrate from one box to another. The lower box is the compost box where you put the worms. Above it comes the vegetable box in which you add fruit and vegetable waste.

The upper box is covered with a lid.

The boxes can easily be taken apart to harvest the ripe compost or percolate from the bottom tray.

DIY stackable box wormery:

You can buy a wormery or make it yourself much cheaper.

That’s actually incredibly easy to do: drill holes in the bottom of 2 of the 3 boxes, about 0.5 cm diameter.

You’ll find tutorials on the internet for very sophisticated wormeries, they are often unnecessarily complicated.

And I would not install a tap: the tap could leak and you never get all of the percolate.

The lid can be left as is or drilled with holes. If you drill holes, you need to cover them with a light fabric or mesh to prevent fruit flies from entering the wormery.

Stackable wormery


Compost worms are not common rainworms but a related species, Eisenia fetida, also known as tiger worm, red worm or Californian worm.

What is the difference?

Ordinary rainworms feed on already well-broken down material and dig deep (up to 3 m deep) while compost worms feed on fresh material and remain closer to the surface.

Where can you get compost worms?

Compost worms can easily be obtained from a friend who has a wormery or garden compost bin, a local compost master or the municipal plant service.

You need a lot of worms to start, about 500-1,000 compost worms. That’s about 5 liters of compost with compost worms.

After 2 months, they start to multiply and you should find cocoons in the compost.


Compost worms do not like light. If you put them in a dark place, you can use transparent plastic bins.

If they are in a light spot, use black or other dark colored plastic.


Place a wormery indoors where the temperature is more or less stable. The ideal temperature is between 15-25 °C.

The garage, basement, a storage room and even the kitchen are fine. As long as you can easily access the wormery to add fresh food or or harvest.

You can also place it outdoors but it will not work as well. If you place it outside, it must be in the shadow and frost free.

How to start a wormery:

Both in the monobox and stackable box, start with a layer of bedding at the bottom, directly above the percolate box.

Bedding layer:

Put a bedding layer on the bottom of the compost box (box just above the percolate receptacle).

The bedding layer consists of airy material such as straw, fine wood chips, fine branches cut into pieces.

This layer allows the percolate to sip in the receptacle.

Starting layer:

Place compost containing worms above the bedding layer. You don’t need to fish them out of the compost they were shiped in as they are very sensitive.

Food layer:

On top of the starting layer, place a 5 cm height of vegetable residues cut into small pieces (max. 5 cm).

The worms feed on the compost they were transported in the first weeks. Meanwhile, your first batch of vegetable waste begins to break down thanks to bacteria and fungi.

After a few weeks the worms begin to feed on that first batch.

Important: as long as the worms have not migrated to that first batch, do not add any fresh food!

And then what?

Once the worms have migrated to the new food, you can add fresh food regularly.

Collect your kitchen waste in a small plastic bucket with lid. Once you have enough for a new 5 cm layer, add it to the wormery.

How do you check the wormery’s health?


In a well-functioning worm bin, most worms are found between 5 and 15 cm deep.

If they are lower, wait before adding new waste.

If most worms are near the surface, give more fresh food.


A good working wormery does not stink. Only the smell of freshly added waste may be present.


In a well-functioning wormery the percolate is dark brown and does not stink.

If the percolate is pale and/or stinks, there is a problem.

What do you do when the wormery stinks?

Stench occurs only when there is not enough air circulating in the material, anaerobic bacteria will then start working and they cause the stench.

Start by checking the depth of the worms in the box: if they are very deep and still live, stop adding new food for a while.

Adding a new bedding layer can also help.

If the worms die, you will need to start all over again.

What may or may not be thrown in the wormery:


  • Vegetable waste from the kitchen, not cooked and cut into 5 cm pieces
  • Coffee grounds with paper filter and tea bags
  • Crushed eggshells
  • Wilted flowers, cut into 5 cm pieces

Not allowed:

  • Meat and fish, whether raw or cooked
  • Prepared food leftovers
  • Pasta: bread, pastry, pasta
  • Excrements from dogs and cats
  • Oil, sauce, mayonnaise
  • Dairy products

Harvesting and use of the percolate:

The percolate can be harvested out of the lower box as soon as there is enough, do not allow the level to reach the compost layer.

You can keep it for months in a dark bottle, out of the light, at room temperature.

This percolate serves as free fertilizer, when watering your plants. It is rich in potassium, magnesium and calcium. It contains less nitrogen and phosphorus.

Never use it undiluted! A dilution of 1/10 percolate with water is recommended.

The percolate must be dark brown and not stink. If the percolate has a pale colored or stinks, check the wormery for problems.

Harvesting and use of the compost:

The compost is harvested once or twice a year.

As the compost is quite wet, place the compost box a few weeks on top of the food box to allow it to dry out.

The worms then move to the underlying food box.

Compost is very rich in nutrients and must never be use pure. It is best mixed with soil.

You may also not sow in pure compost or even in compost mixed with soil. Add compost when the seedlings are large enough to transplant.

Note: Unlike composting in the garden, no heat is developed in a wormery. Therefore, seeds present do not lose their germination power. It may happen that seeds of vegetables or fruit germinate in pots where you added the harvested compost.

Use a maximum of 20% compost per pot, mixed with potting soil, garden soil or coconut fiber.