Photo credit: Earthworms by Petr Kratochvil
Worm Farms are a great way to recycle kitchen waste and food scraps into one of the best garden fertilizers available!
It’s very easy to maintain a worm farm, it takes very little time and effort, and you can set up worm farms in the smallest of spaces, such as balconies and courtyards.
Worms farms are in fact worm composting systems, or more correctly, vermicomposting systems, and earthworms are one of the fastest composters there are.
In this article we’ll discuss how worm farms work, how to set up a worm farm and how to take care of it.
Choosing a Worm Farm
You can buy or build a worm farm, and they come in all shapes and sizes to suit all tastes and requirements.
Most worm farms consist of a set of stacked trays with legs, and don’t take up much room at all. They are ideal in size for a small household.
If you’re after a larger capacity worm farming system, one that can process large amounts of food waste, you can make one out of a recycled old bathtub or buy one of the commercial wheelie bin worm farms. These larger worm farms are ideal for places that generate lots of food scraps, such as larger families, schools, cafes, restaurants or workplaces in general.
It’s important to choose a worm farm that will fit in your available space that can cope with the volume of food waste you produce.
It’s important factor to consider the ‘footprint’ – how much space the worm farm takes up on the ground. As you can see in the picture above, my three worm farms occupy a fair bit of space, luckily it’s in an unused corner of the backyard. I started with one worm farm , then added one more to cope with extra kitchen scraps, and then was given one – it wasn’t planned to run three side-by side!
A bathtub worm farm has a capacity of around 200L, and as you’d expect, it occupies the same space as a bathtub, which is a fair bit of space!
A wheelie-bin worm farm can have a capacity of 140L, 240L or 360L and occupies very little space on the ground. It and has the advantage of being moveable because in has wheels. Consider your requirements when purchasing, and you’ll be well rewarded, as worm farms last a very long time and are a great investment for the organic gardener!
An innovative wheelie-bin worm farm that provides high capacity and occupies very little space, can be purchased complete or as a retro-fit kit to convert existing an existing wheelie bin. (Photo credit: Worms Down Under, http://www.wormsdownunder.com.au , photo used with permission)
How a Worm Farm Works
Worm farms use earthworms to break down organic matter such as food scraps to produce worm castings and the liquid ‘worm wee’, properly termed worm casting leachate.
All earthworms can do the same work, converting organic matter into valuable worm castings, but some breeds do a better job than others, so naturally, we choose the best worms for the job!
The earthworms used in worm farms are in fact compost worms, which are different to the regular earthworms found in garden soil. Compost worm are surface feeders and don’t burrow deep into the soil like garden earthworms do. The various breeds of compost worms, such as Tigers, Reds and Blues, are capable of eating their own body weight in food each day, so a kilogram of worms will consume that much food daily! By comparison garden earthworms only eat around half their body weight each day, so they aren’t as good at composting lots of material really quickly, as it takes them twice as long.
It’s important to keep in mind that compost worms won’t survive in your garden soil. Being surface feeders, they can’t burrow deeply into the ground to the cooler soil in the heat of summer like regular earthworms, so they don’t survive for long. They also need thick layers of composting organic material on top of the soil to feed on, so if there’s no organic matter over your soil that is breaking down, they won’t have any food.
All earthworms are part of an ecological class of organisms called decomposers, they eat rotting organic material and turn it into worm castings. Since they don’t have any teeth, earthworms need to wait till their food start to break down before they can begin to eat it. If their food is chopped up or broken up, it breaks down faster, and the worms can eat it sooner.
Now that we’ve covered basic earthworm theory we can now look at worm farm designs.
Worm farms are usually made from two stacked trays:
- The top tray contains the worms and food scraps.
- It has a lid to keep pests out, with air holes in the lid so the worms can breathe.
- It has drain holes in the bottom which allow any liquid to drip out.
- The bottom tray collects the liquid that drips out of the top tray.
- It has a tap or outlet on one side where the liquid can be collected.
The liner that sits at the bottom of the top tray stops the worms from falling through the drain holes into the liquid below and drowning. In commercial worm farms a piece of cardboard or some newspaper works fine as a liner. In homemade worm farms, where the drain holes are bigger, use a piece of shade-cloth or window screening first, then put the cardboard or newspaper down over it.
The worm bedding is where the worms live, it is usually just a damp layer of coconut coir, but you can use other materials such as damp shredded newspaper, or well-aged compost or manure.
The food scraps are kitchen scraps and other materials that the worms can eat - we’ll go into detail of what you can and can’t feed your worm later on in this article.
The cover which is also called a ‘worm blanket’ is an old hessian sack or a whole newspaper, it helps create a dark, cool and moist habitat by providing a cover over the bedding and their food, which encourages them to move into the food and eat it. The cover will eventually break down after a few weeks as it is biodegradable.
This is the basic worm farm design, but there are some variations. Many worm farm that you buy will have two or more top trays, the idea being that when the top tray fills up with worm castings, you can just add another tray to the top of it, and start putting kitchen scraps in the upper tray, and the worms will move up to the food. That also lets you remove the lower tray of completed castings to use in the garden while the worms are busy eating in the new tray.
Lets have a look at another worm farm design and see how it also works.
Bath Tub Worm Farms
Large scale worms farms made from recycled bath tubs don’t have multiple trays, just a single level. The bathtub is supported off the ground on bricks or it sits in a wooden stand or frame, and a bucket is placed below the drain hole to collect the liquid. The drain hole is covered with mesh or screen so only the liquid comes our. The bottom of the bathtub is filled with coarse gravel for drainage, then the bath is lined with shade cloth above the gravel and then filled with bedding material. The rest of the layers are just like any other worm farm. Since bathtubs don’t come with lids, a timber sheet or wooden cover is used to protect the worms and keep them shaded.
Setting Up a Worm Farm
When setting up a worm farm it is important to choose the right location. Worms like a cool environment, so if you locate the worm farm in a shady spot outdoors where it will not overheat from exposure to direct sun, your worms will be happy.
You can place the worm farm on a shady side of a fence, at the side of the house where there isn’t much sun, under a tree, or even inside a shed or garage as long as it doesn’t get really hot in there during the summer. A protected spot on a balcony will work just fine too.
It’s also important to set up the worm farm in a location where you can easily get to it, so it’s ideal to locate it close to your kitchen, which will be the source of kitchen scraps for your worm farm. If you can’t easily access your worm farm you’re less likely to use it.
The Permaculture design principle of Relative Location explains how to set up a closed-loop sustainable gardening system with a worm farm and kitchen garden
TIP: Keep a small bucket or container with a lid in the kitchen to throw your food scraps into, and empty it into the worm farm when you’re done. Lining with a piece of newspaper helps keep the container clean and the newspaper will be broken down in the worm farm with the food scraps.
To set up the worm farm, it’s quite simple, especially if it’s one you purchase, as they all come with instructions which are similar to those you’ll find below.
Here are the basic steps to getting a worm farm stated:
- Assemble purchased worm farm or construct one yourself (see instructions for building a worm farm here).
- Place the liner (about 0.5cm (1/4”) of newspaper or a sheet cardboard) in the top tray.
- Prepare bedding material (by either soaking coconut coir or shredded newspaper in a bucket of water till it is damp, or acquiring a container of well-aged compost or manure) and put into the top tray above the liner.
- Place the cover (worm blanket) made out of a whole damp newspaper or a damp hessian sack over bedding.
- Add worms onto the bedding under the worm blanket cover, begin with around 500-1,000 worms..
- Allow a few days for the worms to adjust to their new environment.
- After a few days, begin to feed the worms lightly.
What to Feed Your Worms
Firstly, what you feed your worms is important. There are some things that worms won’t eat, and there are other things that are just simply unhygienic to put into a worm farm.
Remember that a worm farm is a vermicomposting system, it is used mainly for food scraps, which break down very quickly. Woody garden prunings and green waste are slow to break down and are better placed in a regular compost bin instead.
Let’s have a look at what you can and can’t put in your worm farm:
Things You Can Put In Your Worm Farm:
- Fruit & vegie scraps
- Bread & cheese
- Cooked vegetables, grains, pasta & rice – basically all vegetarian foods, no meat-based sauces!
- Coffee grounds & tea bags – as long as teabags are paper and not plastic mesh
- Egg shells – great source of calcium, a mineral which worms require in their diet to stay healthy
- Newspaper & unprinted cardboard (soaked) – no glossy printed pages
Things You Can Put In Your Worm Farm (with caution!):
- Vacuum cleaner dust – only if your carpets are natural fibre, not synthetic carpets!
- Citrus & onions – only small amounts or none at all!
- Pet waste – only in a dedicated worm farm for pet waste only
Things You Can’t Put In Your Worm Farm:
- Fish & meat – this will stink and attract vermin such as rats, use a Bokashi bin instead to compost meat
- Garden waste – too slow to break down in a worm farm, put into compost bin instead
- Glossy and bleached paper – this is toxic, you don’t want this anywhere near your garden
- Fresh manures – many animals are treated for worms with vermicides, which pass into the fresh manure and will kill your worms, compost them first!
How to Feed Your Worms
Secondly,how you feed your worms is also very important.
Place the food on the bedding, beneath the cover, also known as the ‘worm blanket’, which is just a damp old hessian sack or a whole newspaper, fold it to fit if necessary.
When you first set up your worm farm, add a small amount of food, and as the worms begin to feed in a few days, then add more. Don’t overfeed your worms as the food will remain uneaten, and will begin to rot, which doesn’t create a healthy habitat for your worms.
When feeding the worms in the worm farm, don’t cover the whole surface with food, place the food to one side only, and try to cover half of one side at the most. Just in case the worms don’t like what you’ve just put in there, they can go to the other side of the worm farm where there;s no food. If you cover it completely they’ll have nowhere to escape to if they don’t react well to your latest food offering. Once that half covered with food is eaten, add more food to the other side, and alternate sides, so there’s always a food free side for them to move to if they need to.
The worms in the worm farm will breed and the population of worms will grow. As they multiply they will eat food faster, and you’ll be able to add more food. The number of worm will eventually self-regulate to match the size of the worm farm and the food available, so after a while you’ll know how much food they can process.
Collecting and Using Leachate
Worm farms all have a tap or outlet to collect the liquid that seeps out from the worm farm, this liquid is often called ‘worm wee’ or ‘worm pee’ but the correct name is worm casting leachate.
To collect the leachate:
- If your worm farm has a tap, just put a bucket under the tap, and turn the tap, the liquid will flow out to fill your bucket. When you’ve collected it all, close the tap, it’s that simple.
- If your worm farm doesn’t have a tap, and just has an outlet (a pipe) for the liquid, then place a small bucket permanently under the outlet to collect the liquid as it’s produced.
Even if your worm farm has a tap, you can permanently leave the tap open and place a bucket under the tap, this will prevent flooding! This is how I prefer to do it, and in the picture above you can see how the liquid fills the bucket after a light rain.
To use the leachate, always dilute it with water first before you use it on your garden, as it may be too strong to use directly. Always dilute it 10:1 with water, that means one part leachate to ten parts of water. When it is diluted it will be the colour of weak tea.
It’s important to keep in mind that the leachate is it is not a fertilizer like worm castings, it’s more of a soil conditioner that improves the health of the soil as it’s full of minerals and beneficial microorganisms. Think of it more as a vitamin tonic for the plants and the soil, rather than a food. Since it’s rich in beneficial beneficial microorganisms, you should always dilute it with rainwater, because tap water is chlorinated and will kill all the good bacteria in there!
Collecting and Using Worm Castings
The worm castings, or vermicompost, are ready to collect when the bedding material and the food in it has broken down well and all that remains is a dark, rich, fine, moist substance, in which you can no longer see the food scraps.
A good time to collect the castings is in spring and autumn, because this is a good time to fertilize your garden.
The trickiest part of collecting worm castings is separating the worms from the castings! You want to keep your worms in the worm farm. There are a few techniques for harvesting worm castings which allow you to separate the worms out which we will look at in detail below.
How to Separate Worms from Castings
The ‘Rainy Day technique’
If you have a worm farm which uses stacked trays, you can wait for a day when it looks like it is about to rain. On rainy days the barometric pressure in the atmosphere drops, and the worms sense this, so they rise to the top to avoid drowning when the rain comes down. This is a natural survival instinct that for when the rain floods their burrows and tunnels in the ground. When they worms come to the top, they will all leave the lower tray, and will gather in the top tray or inside of the lid. When they all come up, you can quickly lift out the lower tray and put it aside for later use. Don’t leave it out in the rain though, as it will become overly waterlogged, and lots of beneficial bacteria will get washed out, put it undercover somewhere and use it in the garden as soon as possible after the rain has passed. With worm farms that have a door at the bottom to harvest castings, simply harvest the castings and put them in a bucket for later use, but don’t leave them sitting in the bucket for an extended period of time, as there’s no drainage and any moisture at the bottom may become stagnant water.
The ‘Pyramid technique’
So what happens if it isn’t going to rain anytime soon and you need castings? Well, there are other habits that worms have which we can take advantage of. Worms dislike light, so make sure you don;t expose them to direct sunlight when caring for them, they sunburn easily! To separate the castings from the worms, gather your castings, which will contain worms, put on some rubber gloves, and place a pile of castings on a low flat container or board, and shape it into a pyramid shape. Do this in a shady spot outdoors. The worms will not stay in the narrow pointed tip, and will burrow downwards to escape the light. Scoop off the tip of the worm casting pyramid, and put that into a bucket. Then reshape the pile into a pyramid with a new tip, and harvest the worm-free castings again. As you keep on doing this, the pyramid will get smaller and smaller, and the worms will keep moving to the bottom. When you have a small, low, flat pile full of worms, put it back in the worm farm.
The ‘Let The Worms Decide technique’
We can take advantage of yet another of the worms natural instincts to facilitate the harvesting of castings. When their bedding turns to castings, they will be basically living in their own waste, which is not their preferred environment. They have a preference for fresh bedding material with a supply of food. If you push the castings to one side of the worm farm to make a space to lay down fresh bedding material, put fresh bedding in in that space, and ONLY lay food on the fresh bedding side, the worms will move over to the area with fresh bedding and food, and will move away from the side which contains only their waste (castings) and no food. Once all the food is finished in the castings, they will decide to move out to the nicer side, and you can then collect the castings! This technique works well in long, wide worm farms such as bathtub worm farms.
In the process of harvesting worm castings, you’ll find earthworm eggs or cocoons. They’re easy to identify, they’re small amber or yellow eggs about 3mm (1/8”) in size which look like little beads but when you have a closer look at them they’re shaped like tiny lemons. Pick these out when you come across them and return them back into the worm farm.
Try to use the castings fairly soon after you’ve collected them, don’t let them sit around for a very long time, and don’t let them dry out, as they’ll lose their beneficial value.
Now that you’ve collected your castings, there are many ways that you can use them.
How to Use Worms Castings
- In the garden – dig into the soil or place under mulch
- Sowing seeds – add worm castings (up to 25% of total volume) to your seed raising medium
- Indoor plants – add to the potting mix during growing season
- Compost activator – add some worm castings to your compost bin to inoculate it with beneficial bacteria, which will help kick start your compost
- Worm casting tea* – made similar to compost tea, full of nutrients and beneficial soil organisms, which can be used as a foliar spray on the leaves or watered into the soil.
Basically, you can use worm castings the same way you would use any slow-release organic fertilizer, it’s that simple!
* Note – How to make worm casting tea (or compost tea) is a process that would take a short article to describe so I haven’t included the instructions in this article!
Worm farms are quite problem-free and easy to look after, but there are a few things to keep in mind that will make caring for your worm farm much easier.
Here’s a few of the biggest problems you might face and some simple solutions.
Unless your worm farms is undercover, it will get rained upon, and some rainwater will get in, depending on the design. This is a benefit in my mind as it flushes out the castings and makes a good supply of worm casting leachate (worm wee) that you can use in your garden.
If your worm farm has a tap, and the tap is closed, then your worm farm may get flooded!
The simple solution is to leave the tap permanently open and place a small bucket underneath as shown below. This will also prevent the tap getting blocked too.
If you do need to leave the tap shut, you can save any worms from drowning if they fall into the liquid in the bottom by giving them and ‘island’ they can climb onto. Just place an upside-down terracotta pot into the bottom of the worm farm where the liquid collects. The terracotta pot is heavy enough so it won’t float and move around, and the surface is not slippery like plastic, which will allow the worms to climb the sloped sides as shown below.
Also, remember to open the tap and collect the liquid from your worm farm once a week, and if your worm farm is exposed to the rain, collect the liquid immediately after it rains too.
The fastest way to lose all the worms in a worm farm at once is to accidentally let them get cooked in hot weather!
We’ve already discussed the location of the worm farm earlier in this article, it should be in a protected, shaded location away from direct sun. Sometimes, even the shadiest location might get direct sun exposure during summer, because the sun is directly overhead, or because the hot west afternoon sun comes in from the side as the sun lowers in the evening.
Worm farms can overheat simply due to the high temperature of a hot summer’s day, because the air outside is hot, and they’re in an enclosed container. To alleviate this problem, prop the lid the worm farm open a bit to let air circulate through and to release any hot air that may be building up under the lid. You can simply lie a stick across the top of the worm farm and place the lid over it so there’s a gap between the top edge of the worm farm and the lid.
On really hot days, you may need to cool down the worm farm by watering it with a watering can and rainwater. Make sure there’s some form of cover material (the ‘worm blanket’) in place such as newspaper over the bedding and food, to keep the worm’s environment dark and moist. Open the tap to prevent flooding and place a bucket underneath to collect the liquid. Water with a watering can making sure you evenly dampen the whole surface. DO NOT use tap water if you can , it is contains chlorine, which will kill a lot of the beneficial bacteria on your worm farm! After wetting down the bedding and cover material, the water will slowly evaporate to create a form of evaporative cooling which will help the worms cool down.
The best way to protect worm farms from direct hot sun is to cover them with a screen of some sort that is light coloured and will reflect the sun, with sufficient air-space underneath it so it doesn’t trap the hot air over the worm farms and cause them to overheat. You can remove the screen in the cooler seasons, and put in in place during the warmer seasons.
I’ve found that cheap reflective plastic tarpaulin sheets, suspended high above the worm farms to allow air to flow underneath, work extremely well. You can tie the bottom of the tarp to a brick or other heavy object to stop it flapping around in the wind.
Pictured below are my worm farms (and a compost bin on the far left) sheltered behind a fence.
It’s natural to have a few other insects in your worm farm, but some are unwelcome guests!
Ants do not belong on your worm farm, and it may be because it’s too dry in your worm farm, as ant’s don’t like moist environments.
To discourage ants, dampen down the worm farm with a watering can full of rainwater, and to stop them getting in there, create a barrier, an ‘ant moat’ by sitting the legs of your worm farm (if it has legs) in tray of water as pictured below.
Worm farm legs sitting in plastic pot trays filled with water form a moat which prevents ants getting in!
The water will evaporate on hot days so remember to keep it topped up. I’ve seen suggestions of using taller narrow containers filled with oil which won’t evaporate but in my mind that will create a disgusting mess as dirt gets blown in by the wind. I reckon water is a much tidier solution!
Smearing a band of Vaseline around the legs of a worm farm is another suggested solution but it’s likely to melt in hot climates.
Ants aren’t a problem unless you overload your worm farm with lots of sugary food, and if the food has been there long enough to attract ant’s there’s a chance you may putting in much more food than the worms can eat. Remember to chop up the food so breaks down faster!
Vinegar flies are those tiny flies that fly up into your face when you lift the lid on a compost bin or worm farm. They are attracted to rotting food, especially fruit, as are fruit flies, so the best way to prevent them breeding is to cover the food scraps beneath a damp newspaper (remember that all important ‘worm blanket’ cover over your bedding!)
Other insects such as millipedes are not a problem, they are decomposers and feed on rotting organic matter, returning the nutrients to the soil. Slaters, also known as wood lice, pillbugs, roly-polys or butcher boys are also beneficial decomposers and are in fact land-based crustaceans! Soldier fly larvae, which look like giant silver-grey maggots are also beneficial, though they look a bit creepy. Springtails are unmistakeable little insects which hop around on the surface when you lift the lid, they are also beneficial, they’re all part of the decomposer community too, a natural part of the Earth ecosystems recycling processes.
If you see tiny white worms in your worm farm, they are not baby earthworms, these worms are entrachyadids, they are not harmful but do indicate that your worm farm has become a bit too acidic. Correct the acidity by sprinkling a small amount of garden lime, dolomite or wood ash (which are all alkaline) in your worm farm every few weeks.
Smell & Odour
A healthy worm farm will have little to no smell, perhaps a faint but pleasant earthy smell just like healthy soil or a forest floor. If it has a sharp vinegar smell it may be too acidic, add crushed eggshells, garden lime, dolomite or wood ash to correct the problem.
If it smells quite offensive, it is an indicator that the system has become quite anaerobic from too much uneaten food. To fix this problem, stop adding any more food, add a sprinkling of garden lime, dolomite or wood ash, and lightly stir up the existing food scraps to aerate them on a regular basis. Once the smell disappears, then begin feeding the worms again.
So, as you can see, it’s quite straightforward to run a worm farm, it doesn’t take much effort to keep your worms happy.
Your worm farm will give you a free supply of valuable castings and leachate for your garden, which your plants will absolutely love!.
Time to get worm farming!
If you don’t have a worm farm, and you’d like to build a quick and easy worm farm in a few minutes, please take a look at our article on Building a Broccoli Box Worm Farm.
If you like the idea of a very low maintenance In-ground Worm Tunnel Worm Farm that sits below the ground, please check out the article Build a Worm Tunnel Vermicomposting System