Why worm farm?

Anyone can start a worm bin. All you need is a suitable container, bedding material, and of course, worms.

Help the environment
Organic matter thrown into landfills is broken down by bacteria and results in methane and carbon dioxide, gases that we don't want in the atmosphere. NZ has somewhere around 1000 landfills which have an impact on our environment. The more organic waste is diverted from landfill, the better.

It's fun and easy
Anyone can make a worm bin and maintain it. They don't take up much room, (even people in city flats can own a worm bin).  Worm bins don't smell, and kids love them!

Free fertilizer
Why pay for it when you can make it yourself for free. Worm casts and liquid are abundant in phosphates and nitrogen. Watch your plants bloom and grow!

Keep it in the loop
Put back the energy and nutrients back into the ground that you took out of it.

Save $$$$$
Around 45% of an average rubbish bag is filled with organic matter that could be composted or worm farmed. Why pay to dump it?

Vermiculture or worm farming

Worms break down and eat a lot of organic matter and excrete it as casts (vermicasts, or 'worm poo'). Verimcasts are richer than many fertilisers (the casts contain 5 times more nitrogen, 7 times more phosphorous and 12 times more potassium than the soil) and are better than the same commerically available chemicals derived from petrochemicals.  "Worm tea' or  'worm juice' is similarly high in nutrients and is prized as a liquid plant food.
Worms prefer temperatures of 18-23 °C, although they can tolerate 10-30°C. It is best to place your worm bin (or worm farm) in a shady spot. This could be in the garden, on the porch, garage or deck. 
It is very simple to keep a worm bin - they don't need to be walked, and they don't need feeding that often, so you can go away on holiday and not take them with you!  Ours at the Environment Centre have been abandoned during holidays for up to 2 weeks without illhealth.

What do I feed them?

Worms do not have teeth but a muscular mouth and oesophagus which pushes the food down into the gut. Glands inside the worm excrete calcium carbonate onto the food to assist break it down.

Worms eat most organic matter (things that were once living)and as long as the food is damp and small enough. But there are things to avoid:

Tea bags

Coffee grinds

Paper (not too much coloured ink)
Vacuum cleaner dust
Dried leaves
Small amounts of grass clippings
Small amounts of citrus
Egg cartons
Egg shells
If adding carpet, make sure it is washed off first, so no detergents enter the bin
Food scraps



Spicy foods
Pine needles
Sawdust (it may be treated)
Bread (only small amounts should go in)
Large amounts of citrus

Worm Bio

Worms are hermaphrodites (both sexes on the same worm) but require another worm to mate with. They lay eggs in a cocoon which hatches into the soil in 3 weeks. Each capsule contains 3-5 baby worms (sometimes more).
Respiration occurs through the moist membrane (skin) which is another reason why the environment for the worm must be kept damp.

It is a fallacy that worms chopped in half will regenerate. A worm's internal organs are spread along its body. It also has a closed-circuit blood system. Once severed the worm will continue to live until the organs are starved and then it will die.

Which worms, and how many?

Composter worms (usually Tiger worms or red worms) are best for worm farming. Composter worms live at different depths and eat different things, to earth worms. Earth worms (usually the thicker grey worms found in lawns and gardens) are not ideally designed for composting and should not be used in a worm farm.

  • 1kg of composter worms equates to around 4,000 worms.
  • 20,000 composter worms can digest food created by a family of 4.
  • 10,000 worms will eat around 20 kilos of food producing 12 kilos of vermicasts.
  • A kilo of worms can eat through 500g of organic waste every 24 hours.


When preparing your worm farm or bin, leave the bottom catchment tray empty for the worm juice to collect in.

Add bedding to the second bin. Bedding may be composed of a mixture of compost, soil, potting mix, hay, a small amount of grass clippings, paper and cardboard and food scraps. The bedding needs to be porous, loose, damp, and partially broken down before the worms are added. As with composting some air is needed to enter the bin.

Occasionally you may need to add a small amount of lime to the bin to keep the pH neutral. A small handful every month should be ample (try not to get it on the worms).
There are several worm bins on the market. Can ‘O' Worms is a really good system, but you could also make your own worm farm out of an old bath.


After a couple of months the contents of the bin break down,  are processed by the worms and castings produced.
There are different methods of removing the castings depending on the bin. For a 'Can-O-Worms', you need only add a new tray containing food scraps - the worms will migrate from the tray below, allowing you to remove and use the castings from the lower tray. For other types of worm farms you may have to remove the castings by hand - feed the worms on one side only, and take out the castings from the other side.
 Liquid should be collected and extracted from the bins. Before using worm liquid in it will need to be diluted 10:1 (i.e 10 litres of water to 1 litre of worm liquid).

Trouble shooting

Smelly worm bin? Over feeding, not balanced. Try reducing food and keeping a balance by adding more paper (carbon stuff) than food scraps (nitrogen).
Vinegar flies?
 They are after citrus and fruit. Cover the bin and add a handful of lime.
 These are a natural part of the process and help break down food.
Tiny white worms?
 These are called entrachyadids and indicate acidic conditions. Lime again!
Too many worms?
  Sell them!


  • There are around 200 species of worm in NZ. However, only about 10 species are valuable to agriculture.
  • Worms mate every 7-10 days (producing approx 50 eggs per year)
  • Worms mature in 60-90 days
  • Worms ingest and excrete their weight once a day
  • Life span several years (15+)
  • Worms have 5 contractile hearts
  • A mature worm at 60 days old can produce over 1,200 young each year

Where do I get worms from?

If you have access to a compost patch (either yours of that of a family/friend/neighbour) then you can try foraging for red worms living in the composting layers of the compost patch.  This could be an ideal fun job for children.


Waikato Environment Centre - phone us on 07 839 4452.  We have a list of suppliers for you

Other sources:
Kiwi earthworm    
Xtreme Waste      

Where do I get bins from?

Waikato Environment Centre: We have sevral models in stock, including the giant Hungry Bin

You can also buy worm bins from The Warehouse (all stores), Payless Plastics, Mitre 10 stores and some hardware retail outlets. Check online at sites such as Trade Me:

Worm farms can easily be made from a recycled kitchen sink or bath obtained from your local waste exchange - for example Xtreme Waste in Raglan sets aside suitable worm farm "equipment" for purchase: simply contact them for further information. 

More Info?

See our "Related Page" below.

Photos gifted by CK Reynolds.

Worms galore!

Worms galore!