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Compost Worms

What are Worms?

Worms are the great recyclers and aerators of our soils. They work tirelessly in nature to turn dead and decomposing organic matter into rich, healthy soil that is full of life. On the urban farm we can harness the humble worm’s power to vermicompost or recycle organic waste. We can do this in the ground or in the compact and incredibly efficient composting system, the worm farm.

Worms in a worm farm
Worms can live in a very high density in a worm farm.
Before we move on let us get a bit more scientific about what a worm actually is. Worm is a fairly loose term zoologically and could refer to any number of groupings. When I use the word here I am referring to the segmented earthworms of the phylum Annelida. Of the earthworms there are those species that really do live in the soil (more on these later) and those that live in leaf litter called compost worms. Compost worms are the type that do best in worm farms.

Species of Compost Worms

In Australia the most common compost worm species are red tigers (Eisenia fetida), reds (Eisenia andrei), blues (Perionix excavatus or P. spenceralia), gardener’s friend (Amynthus sp.), European night crawlers (Eisenia hortensis) and African night crawlers (Eudrilus eugeniae). Suppliers will provide you with a mix of some or even all of these species. If your aim is simply to vermicompost then any mix of species will do though red tigers surely are the king composters. If you plan to turn over a lot of kitchen scraps make sure your mix has some red tigers. If on the other hand you intend to use your worms as fishing bait then you need to ensure that you are keeping one of the larger species as well. My personal favorite fishing worm is the Indian night crawler for its wide tolerance of temperatures (unique among the large worms).

Keeping a Compost Worm Farm

Worms are perhaps the easiest livestock to keep on the urban farm. Even the apartment dweller can live more sustainably by keeping a worm farm for processing kitchen scraps and as a source of fishing bait. Worms also make great poultry food or even another income stream on the homestead. People are always looking to buy worms so they can get started on their own worm farm at home. Of course their casting are one of the best organic fertilisers you will find anywhere. There are a lot of reasons to keep worms!


Worm Cafe worm farm
Worm Cafe worm farm. Very representative of the many small home scale worm farms available.
At its core all a worm farm really needs to do is contain the bedding and drain well. If you want to collect the farms waste water then the system also needs a way to do that without drowning the occupants. The worm farm itself can be as simple as Styrofoam boxes stacked on top of each other or as complicated as the large flow through systems that are used commercially. If you are just getting started with keeping worms then a Styrofoam DIY model is a great way to test the waters with minimal to no outlay. If you decide to upgrade then transferring your growing numbers is no big deal.

Worm Habitat worm farm
Worm Habitat worm farm that we use at Pobblebonk Patch. If you have an old bin you can make your own using a kit from Worms Downunder
At Boobook Farm we use wheelie bins that have been modified with a raised mesh floor and a tap in the bottom. There is also an extraction door added down low and vents have been placed around the top of the bin. This system works well but the tap has to be kept sideways at all times or the bin raised off the ground as it is just too low. My parents and brother’s family use a smaller, single, commercially manufactured systems that we gave them. These are a step up from the Styrofoam worm farm in terms of durability and allow you to easily collect and store the worm pee until you want to use it (more on this later). One word of warning though. Throw away the keeping instructions that come with these systems and read this article instead. Many systems fail because of instructions given with these systems.

Whatever worm farm you end up using, where you place it will be crucial. Worms have the capacity to move around their worm farm to get away from hot temperatures but that is as far as it goes. If it gets too hot then that is the end of your worms. Cold isn’t great for your worm farm either but in a sub tropical climate it is always better than direct sunlight. If you are in the tropics or subtropics then er on the side of caution and place your worm farm in all day shade. If you are from a colder climate then some morning sun might be beneficial in the winter.

Worm farms for sale at hardware store
Worm farms and accessories for sale at my local home hardware store.


Worms cannot live happily in food scraps alone and this is where many home worm keeping projects fail. If you only provide food scraps to your worms you will very quickly create a smelly, anaerobic mess that will kill your worms. Worms need a high carbon bedding material to which food is added in a controlled manner. At Boobook Farm we use dry grass clippings and coffee grounds. You can also use shredded paper, dry leaves, compost or dry manure.
The bedding should be kept moist but not wet. Worms breathe through their skin and if their skin dries out they die. I very rarely add moisture to our worm farms as the scraps we feed the systems provide all the moisture they need. If you do find out your worm farm is drying out then simply add a cup or two of water to the top of the substrate. If you want to get fancy then you can use a spray bottle but really this is not necessary. Don’t forget to add more bedding over time as you remove volume in the form of worm castings from the system.


The basic rule when feeding worms is that they will eat roughly half their weight in food every day. This means that if you start with 500g of worms then they should consume about 250g of food daily or 1kg every four days. This is great on day one when you know exactly how many worms you have but what about three months in? For this reason I don’t try and work out feed rates mathematically. Simply feed less if they are not getting through it within a few days and feed more if they are consuming it too quickly (in less than a day).

In terms of what your worms can eat their are some rules. Firstly they will of course eat the high carbon bedding material and so it is good to add more of this periodically. Vegetable and fruit matter is almost all ok though large seeds (think avocado or mango) will take a long time to break down and are better off in a hot composting system. The only vegetables and fruit that should not be added are onions and citrus which are too acidic. Egg shells are another great addition and provide the calcium that worms need in order to reproduce and lay eggs. Meat of any type is a no go as are bread products in all but the smallest amounts. Both will spoil and make a large mess before the worms can break them down.

Worms have no teeth and so do not bite their food. They need to wait until it is soft through decay or look for very small pieces. For this reason it is good to grind up the food (especially egg shells) or cut it up into small pieces before feeding to the worms. Every cut you make increases the surface area of the food and so shortens the time needed for processing by the worms. Another way you can speed up the process is to freeze scraps and then defrost them before feeding. This breaks up the food on a cellular level and saves the worms some time.

How to Use the Worm Castings and Worm Wee

Worm farm showing worm castings
Worm castings in a worm farm. Note that some scraps like egg shells can take longer to break down if not first broken up into small pieces.
Both worm castings and wee can be added to the garden wherever you want to increase fertility. You cannot burn your plants roots with either so go nuts and add as much as you can get your hands on. To a point of course, don’t bury your plants! I tend to use castings a lot in the nursery when potting up plants or in the vegetable garden. It makes the ultimate organic fertilizer for these sensitive plants that are growing quickly.

The worm wee I refer to is the liquid collected from the worm farm. It is not really wee but a mixture of fluids that has passed down through the worm castings to the base of the worm farm. It does contain a great array of essential nutrients but not in the amounts you might expect. I simply dilute it in a watering can and water my young trees with it. The dilution is not necessary but this helps me to spread it around. Many organic gardeners praise worm tea, a biologically active concoction made by aerating a barrel of water with a worm castings tea bag. Worm tea is an amazing fertilizer and does contain a large amount of life but I do not use it. In terms of nutrients the process does not make them out of thin air. By this I mean that all nutrients were already in the castings and you could have just used that on your plants. My soil has plenty of of the required soil life and so I wouldn’t take this energy intensive step for that purpose either.

When you are using worm castings on the garden and getting the amazing results you deserve remember to pat yourself on the back. You have taken what was a waste stream and have turned it into a wonderful resource for growing food. If you don’t yet have a worm farm get one today.

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