The first thing you'll need is a container made from plastic, wood or metal. Use your imagination and recycle an old bathtub, wooden box, drawer or plastic bin. You can buy ready-made worm bins from garden centres.
Tips for choosing a container:
- Wooden containers provide good insulation but plastic containers are lightweight and convenient
- The container should be at least 20-40cm deep with a surface area of about 40x60cm
- Drill or punch about 10 holes of 10mm diameter in the bottom of the container for aeration and drainage - worms need air to live. If contents become too wet, drill more holes.
- Raise the bin on bricks or wooden blocks to help air circulation and drainage
- Loosely cover the bin to keep in the moisture and provide a dark environment for the worms
- If your bin is indoors, use sacking or similar material on the compost surface or black plastic sheeting on top of the container.
- If your bin is outdoors, use a lid or cover to keep out scavengers, predators and rain.
Choosing your worms
Worms live where there is a good supply of organic matter. To collect worms for your farm:
- Look in a compost heap (they usually like to live in there)
- Visit a horse stable or a farmer with a manure heap
- Search the internet regarding 'Worm Farming' for suppliers near you.
Two species are well suited for worm composting:
- Tiger worms (Eisenia fetida)
- Red wriggler or manure worms (Lumbricus rubellus)
These worms thrive on moist organic materials like food scraps, and eat their own weight per day! Start your worm farm off with at least 500g of worms.
Setting up the worm bed
Worms need a moist bedding to live and lay their eggs.
Suitable materials are:
- Moistened newspaper torn into 25mm strips (avoid coloured print if possible)
- Aged manure
Experiment with different materials. A mixture of ingredients is okay. Fill three quarters of the bin with bedding that has the consistency of a squeezed out sponge.
Add 1-2 handfuls of coarse sand or topsoil. This provides grit that worms need to grind their food.
What to feed your worms
Worms eat plant and meat tissue, so they'll compost most organic kitchen waste. Here’s what you should and shouldn’t feed them.
Good worm food
- Vegetable and fruit scraps or peelings
- Shredded paper or paper towels
- Tea bags or leaves /coffee grounds and filters
- Egg shells
- Bread and cereal
- Plate scrapings - all leftovers, even ice cream!
- Meat and fish scraps and dairy products
Bad worm food
- Citrus or acidic fruits such as oranges, lemons, grapefruit and kiwifruit
- Garden waste (better in your normal compost bin)
- Fats, cooking/salad oils and oily foods
- Tough woody material unless chopped into small pieces
- Onions, garlic or hot spicy food scraps
- Remember: worms don’t like bones, glass, plastic or tin foil.
Harvesting the compost
After 3-4 months the food waste turns into worm compost, ready for use on your garden. This means it's time to harvest.
The easiest way to do this is:
Scoop out the top 150mm layer (this is where the worms are) and set it aside for a new bin
Remove the compost you want to you use on your garden
Put the top layer back into the container with fresh bedding and start a new worm farm.
Be careful that the worms don't dry out. Watch out for baby worms and the tiny oval-shaped cocoons, which may contain baby worms.
Using the compost
Worm compost is an excellent, nutrient material for container plants or combining with potting mix. Use it every time you plant – mix a handful into the soil.
- Keep worms moist but not soggy. If they dry out they will die, or if it's too wet they will drown
- Kitchen food waste is generally pretty moist. but to prevent sour and slimy conditions (creating odours and attracting flies) add food regularly rather than in large quantities
- Add some dry mulch material now and then - fine chip mulch or straw is great
- Chopping or mincing food scraps speeds up the process
- Crushed eggshells should provide enough calcium to stimulate worm reproduction. A monthly sprinkling of dolomite or garden lime can also help boost calcium levels.
- Bury food in the bedding to prevent fruit and houseflies
- If your worm farm gets smelly it might mean the worms have been overfed, the bin is too moist, or the bedding is packed down, limiting airflow
- Watch out for food with seeds such as pumpkins or tomatoes. As worm composting doesn't generate heat, seeds may start growing!