Worm farm

Tips and tricks for looking after this mini-ecosystem in your backyard.

How a worm farm works

A worm farm is a contained system where specific types of worms eat your food scraps and process them into nutritious soil.

To get started, watch this worm farming for beginners video:

Setting up a worm farm

Worm farms can be purchased or you can make your own by repurposing items such as old bins or a bathtub.

You'll need composting worms (such as tiger worms). They can process large amounts of food scraps which is too rich for earthworms. Worms can be purchased at some hardware stores or online. A 250 grams box is a good amount to start with. The worm population is self-regulating, so you don’t need to worry about them becoming over-crowded.

Required space

The average footprint of a worm farm is around 60 centimetre long by 40 centimetre wide (the size of a banana box), making them small and versatile. They can be placed outside in a cool shady site sheltered from the sun – carports, patios, or sheltered porches are ideal.

What you can put in

  • Chopped fruit and vegetable scraps
  • Crushed egg shells
  • Coffee grounds
  • Tea leaves
  • Plastic-free tea bags
  • Bread and baking products
  • Leftovers (that don’t have too much meat and dairy)
  • Pasta
  • Rice
  • Nuts
  • Cereals
  • Poo from herbivorous animals (such as rabbits and guinea pigs)
  • Soft twigs
  • Dried leaves and garden trimmings
  • Cut-up cardboard
  • Paper
  • Paper towels
  • Tissues
  • Wood shavings (untreated).

What you can’t put in

  • Poo from dogs and cats
  • Oil and other liquids
  • Citrus fruits
  • Large amounts of meat
  • Bones
  • Dairy products
  • Chillies/spicy food
  • Onions
  • Garlic
  • Shiny or laminated paper and card.

How to predator proof your system

Most store bought worm farms are closed systems making them predator proof, however if you make your own worm farm, it’s important to ensure any openings where mice and rats could get through are covered with galvanised wire mesh (holes no larger than 1.25 centimetre). On Predator Free NZ website you can find some simple steps to rat proof your compost bin.

What you can do with the finished product

A type of soil called 'worm castings' is created that can be used as a top dressing for pot plants and garden beds. Liquid, known as 'worm tea', is also passed through the bins, which, once diluted, makes excellent plant food.


If you want to learn more about composting, download these guides:

How to set up and maintain a worm farm (139KB PDF)

What can and can't go in your worm farm – reference guide (619KB PDF)

Contact us

If you have a question about composting you can email us at waste.education@wcc.govt.nz