Composting Worms

Let’s start with some trivia on composting worms …

Did you know?

–   Composting worms can eat about half their body weight in one day – to give you an idea 4,000 worms with work through about 2-3kg of waste in a week

–   The most common composting worms in the garden are red wrigglers, tiger worms and Indian Blues

–   If the space is available and the worms have plenty of food their population can double in size every couple of months, however they will eventually max out the population to the size of the worm farm

–   Worms are hermaphrodites, meaning that each worm has female and male sex organ.  Every worm has the ability to lay eggs and reproduce, however they are not self-fertile and reproduction will only take place with adult worms of the same species.

–   Without going into too much detail, the worms mate by wrapping themselves together, secreting mucus from the saddle area (the part that looks like a band) and injecting sperm from the male organ.  The result is a fully encased capsule which contains up to 20 eggs.

–   After about 1 month, only 20% of the capsules will produce in the order of 4 offspring per capsule, resulting in about 1 dozen baby worms per adult every week.

–   Worms are ready to reproduce after 1 and a half to 2 months


Differences between Earth and Composting Worms

The earthworm specialises in consuming dead organic material found on the surface of the soil.  It breaks down the material as it works down to the root base of plants, leaving a nutrient rich soil (castings), which improves the health of the soil and plant.  Earth worm activity loosens heavy clay soils improving the nutrients, aeration and drainage.

Composting worms are not the same as garden earthworms.  They consume large amounts of fresher organic matter such as manure, mulch and green waste and live much closer to the surface of the soil.  Preferring wetter conditions, the composting worms work through the waste and turn it into castings (worm poo) accelerating the composting process of the organic matter.  The castings provide valuable nutrients and minerals to the surrounding plants to absorb.

Why it is a good idea to farm worms?

The number one reason is that you are recycling your waste and reducing your contribution to land fill and as a result reducing methane gas emissions. 

Secondly the end product of worm wee (tea) and poo (castings) is liquid gold for improving your gardens soil structure and feeding the plants.

As your soil structure improves it will increase in its ability to hold water reducing your need to water as frequently.

Finally, worms are one of the easiest pets you can keep – they are quiet, require little maintenance and attract plenty of interest with the kids, especially during feeding time.

Setting up a worm farm

Worm farms can be bought as kits, or you can make your own.  We dispose of our kitchen scraps in a small worm farm kit and also in the wicking worm beds.

You can start out by buying the worms, or simply collect a couple of handfuls from the garden, but make sure the worms you collect are the composting type (close to the surface) as you will need these to break down the waste quickly. 

Most worm farms are set up as follows:

A box to hold the worms in that is well insulated from the sun.  Some examples are:

  • Wooden box
  • Polystyrene container or containers stacked on top of each other for a larger worm farm
  • Old bath tub

The layers (from the bottom to the top) should consist of the following:

The first layer for the worm’s home consists of materials such as:

  • Coconut fibre
  • Chopped up cardboard (shredded egg cartons are great for this)
  • Shredded bark

Note that the above materials will need to be moist to provide the right environment for the worms to thrive in.  Keep this layer nice and thick so the worms have plenty of room to move and breed (the more space you make, the more the worms will multiply to fill the space).  Most worm farms will have some kind of drainage system below this layer to collect the “worm tea” which is all the worm waste.
The second layer consists of a thin layer of straw or grass clippings for the worms to move through to get to their food.

The third layer has partly broken down compost for the worms to get started.  Keep this layer nice and thick as well (a couple of inches).  Then add the worms to the top of this layer and watch them burrow down as they get to work.

The final layer is your food waste.  It is recommended not to include meat, dairy and bones as these will attract unwanted guests such as rodents and ants.  Citrus is also not recommended, however I have found a small amount of citrus does not cause too many issues as long as you add a little lime to reduce the acidity.   As you should not add meat and dairy that is not already broken down, this is where the Bokashi system of composting is useful.  With Bokashi, you can add everything (except the bones), let the food ferment, then add the broken down mix to your worm farms.  Keep adding a good diversity of food in smaller amounts to keep the worms interested and give them a balanced diet.

After you have added the food scraps – cover this layer with some damp newspaper, a hessian bag or some old carpet to keep the environment moist and dark. 

Locate your worm farm in a cool shady spot that is not exposed to the weather.  Some ideal locations would be under a tree, under the veranda, close to the kitchen for easy access.

Feeding your composting worms

Try to add a small amount of kitchen scraps to your worm farm every couple of days.  Monitor the amount of food left over before adding more.  If the food is being consumed, then try adding a little more to encourage population growth.  If you find there is uneaten food in the worm farm that is starting to smell and rot, then wait a few days for the worms to work through this before adding more.  If uneaten food remains, then you know you have overfed the worms.  As mentioned earlier try to mix up the food that you feed your worms – this is usually easy as your kitchen scrap will usually provide enough diversity. 

As I collect a lot of coffee grinds for composting, I learnt the hard way by adding too much of the grinds to one of my wicking worm beds.  As the grinds were breaking down, they heated up and cooked the whole farm, forcing the worms out into the garden bed (fortunately not killing them) and it took a couple of weeks for the worms to come back again.  I have found that broken down coffee grinds are a great worm food – so compost the grinds first before adding to your worms farms.

Using your “worm tea” and castings for the garden

Make sure your worm farm is able to drain freely from the bottom, and has a collection point, so you can use the worm tea to fertilise the garden.  It is recommended to dilute the worm tea with water – however the tea will not burn the plants if it is added as is.  The reason for diluting the tea in water is to spread the mix over a larger area of your garden.  I usually drain the worm farm (from a tap) every week and dilute the tea in a 10L watering can.  This combined with the Bokashi water provides a great fertiliser for the vegetables and fruit trees.

When preparing garden beds for new planting I like to scoop out some of the worms with castings and eggs and then add them direct to the garden bed.  This way I am increasing the number of worms in the garden and also encouraging the worms in the farm to continue to breed and fill the space.  Please use gloves when handling the castings and wash well afterwards.

Another great way to help break down your compost bins is to add a few handfuls of worms.  This works great in my in-ground compost bin, as the worms are able to move into the garden if the mix gets too hot. 

Problems you may encounter

Vinegar flies

This is usually a result of overfeeding your composting worms and having excess food rotting on the surface.  Try adding some more neutral organic matter such as shredded cardboard, newspaper or straw and hold off on the feeding for a while until the worms have eaten the food.  Vinegar flies thrive in acidic conditions, so adding a little lime to the worm farm will also help.  Another method for trapping the flies is to use apple cider vinegar in a container place near the worm farm to trap the flies.


This is usually a result of conditions being too dry.  Keep the worm farm moist (but not too wet).  It can also be because of acidic conditions, so adding some lime to the farm can help with this.  If you can isolate the farm from the ground, then the ants will not have a path to climb in.  If your worm farm is on legs, then you can use buckets of water to help isolate the farm from the ground and prevent ants climbing up the legs.

Smelly worm farm

Again, this will be the result of too much feed.  Keep an eye on how quickly your food is being eaten and then feed small amounts regularly, building up the amount as the worm population increases to fill the space.  Also use the same strategy as for the vinegar flies.

  Benefits of a composting worm farm

  • Worm castings / tea for the garden – No need to buy additional fertiliser
  • Education for the children on how to recycle and care for environment
  • Reducing our contribution to landfill
  • Increase overall health of garden soil as you can regularly add worms from the farm to the garden
  • If you have an aquaponics system, the worms can be used as a food supply
  • Low maintenance

I use one freestanding worm farm (shown below) along with a couple of worm farms in our wicking worm gardens


This is combined with hot composting, normal composting and Bokashi methods to use up all our kitchen scraps plus some extra waste from elsewhere such as coffee grinds (from workplace), grass clippings and dried leaves (from neighbours) and mulch from our fruit and vegetable plants.

The best way to start out is to start small and experiment a little.  Once you are successful with a small worm farm expand to a larger one that is able to take all of your kitchen scraps and enjoy the benefits of a much healthier garden!