All worms eat rotting, organic matter. In the process, they aerate and cycle nutrients and minerals, digesting them with their bacteria, and turning them into castings, producing a great fertilizer. This makes the nutrients easier for plants to process by converting them into a more soluble form. Worm farms are convenient for producing a substitute for compost, can be used in potting or seed raising mixes, and are useful for recycling kitchen scraps. And, if done right, they don’t produce any bad smells.
However, not all worms can be used for worm farms. Worm farms can only house compost worms (such as red and blue wrigglers or tiger worms), which are surface feeders and don’t burrow deep into the soil. They can eat their own body weight in a single day, meaning a kilogram of worms will eat that much food daily. If their food is chopped or broken up, then the worms will be able to eat it faster. Earthworms, by comparison, only eat half as much food and cannot survive in this system.
Worms like a cool environment, so put the worm farm in a shady spot outdoors, preferably in Zone 1 near your kitchen or house. In wet climates, shelter the farm from the rain and shade it from the sun. In cold climates, don’t feed the worms during the winter as they will go dormant and the food will rot. In arid climates, water as needed with rainwater, but DO NOT use tap water, as it may contain chlorine which kills beneficial bacteria. 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 necessary. Lining it with a piece of newspaper helps keep the container clean, and it will be broken down in the worm farm.
Types of Worm Farms
The Styrofoam Worm House
This version has layered boxes with holes drilled in the bottom for drainage. The worms can also crawl up the sides of the containers (or on an island in the center), and travel in between the containers through the holes. The bottom box should have no holes in it, as it captures the worm juice to use as fertilizer.
The Worm Tower
Take a large pipe (no smaller than 20 cm wide), and drill holes into it of various sizes along one half, and fit a clay pot or saucer on top. Insert it vertically into the ground with the holes submerged under the surface so the worms can travel into the tower to eat the kitchen scraps. Insert some aged or composted manure at the bottom and pour the worm castings into and around the pipe. Add the worms, soil, and vegetable scraps on top, and plant around the pipe. Cover it with a flower pot to seal in moisture and keep out pests.
Stacked Bin System
Take 3 or 4 stacked bins (large plant-pots, yogurt tubs, storage bins, or trays), and fit them together so large flies can’t get in, but keep them loose enough so that they can slide. This will allow the top bin to rest on top of the castings in the tray beneath it. Make sure the top tray has a lid to keep pests out, as well as air holes in the sides so the worms can breathe. The top tray should also have holes in the bottom to allow the liquid to drip down to the tray below.
The worms live in a layer of castings and soft materials called the worm bedding, kept in the second tray from the top. When food is placed over this bedding, the worms will migrate up to eat it. Prepare the worm bedding by soaking coconut coir, or shredded newspaper or cardboard in a bucket of water, or get some well-aged compost or manure, and put it into the top tray above the liner.
Place an additional ½ cm, or ¼ in. of whole, unshredded newspaper or sheet cardboard in the top tray above the worm bedding. This acts as a liner or cover, also called a worm blanket, to create a dark, cool, and moist habitat, and also to reduce evaporation. As an alternative, you could use an old hessian sack, or an upside-down carpet. Place this cover over the bedding where the food is. The bottom tray should also have a liner made from cardboard or newspaper that sits on the bottom to stop the worms from falling through. If that is not enough, first lay down a piece of shade-cloth or window screening, then put the cardboard or newspaper on top of it.
When the farm is ready, mix some compost and scraps in the top tray, add about 1000 worms, and cover them with the worm blanket. Allow the worms a few days to acclimatize to their new environment, and then begin feeding them lightly by adding kitchen scraps. As the worms eat the food, they will convert it into castings. When the top tray is about 2/3 full of castings, remove the bottom tray and empty any castings from it. Then move it up to the top, and add new food inside it. The worms will migrate up the sides of the bin from the second tray to the tray with the new food above it, leaving their castings behind for easy collection. Make sure the castings containing the worms remain moist at all times.
Bathtub worm farm
Take an old bathtub (use an acrylic bathtub to reduce weight) and measure about 10 cm up from the base. Then, at the same level as your measurement, cut four or five 10 cm long slots with an Angle Grinder into the sides, going horizontally and parallel with the ground. Alternatively, you could also drill ten 5 mm holes on each side, half way up the walls of the bath. These are to increase aeration into the soil for the worms. Make a frame with timber, concrete blocks, or railway sleepers to raise the tub to a comfortable height off the ground, and high enough to fit a 1 or 2 liter bucket underneath. Level the tub and roll a marble down the bath to make sure water drains out the plug.
Cover the drain hole with 5 mm of gauze, chicken wire mesh, or a screen. Cover it with a 5 cm layer of aggregate (blue metal), coarse gravel, pumice, or scoria as a drainage medium. Next, line the base of the tub with about 5 cm of aggregate or gravel. Then, line it with a shade cloth above the gravel, cut to fit so that it is overlapping up the sides about 10 cm. Lastly, fill with a 5 cm layer of starter bedding material. You could also lay down a wood grate, covered with chicken wire, to create a draining area to allow for the collection of the worm tea. Use a staple gun to fasten the chicken wire to the timber frame in the tub to prevent it from getting loose and shifting around.
Next, fill the tub with a mix of 2/3 aged manure and 1/3 kitchen scraps or prunings. Alternatively, you could fill it entirely with compost. Add 1000-2000 worms, and cover the opening with a light lid (like upside-down carpet or hessian) that will allow rain to drain through. To ensure vermin do not get in, use corrugated iron or plywood as a roof. Let it sit for 3 months, adding about 20 liters of scraps weekly during the summer so the worms will have enough to eat. Then, open the lid, remove any fresh scraps, and put down some chopped scraps at one end and re-cover.
To reduce waste and control the flow of the leachate, add a tap to the flow pipe coming out of the drainage hole. Remember to open the tap and collect the liquid from your worm farm once a week, and collect the liquid immediately after it rains.
How to Use Worms Castings
The castings and leachate make for an invaluable fertilizer for food crops, containing approximately:
- 7 times the available phosphorous
- 6 times the available nitrogen
- 3 times the available magnesium
- 2 times the available carbon
- 5 times the available calcium
Collect the liquid from the bottom and dilute it with pure rainwater (not tap water) to a ratio of about 10:1 (ten parts water and one part leachate), until it takes the color of weak tea. Use worm castings the same way you would any slow-release organic fertilizer. Simply spray it onto the leaves, or use it as liquid soil conditioner (not a standalone fertilizer) to improve the health of the soil.
A good time to collect the castings is in spring and autumn, since this is the best time to fertilize your garden. Cover the castings to keep them damp, and always use them as soon as you collect them. In the process of harvesting worm castings, you’ll find earthworm eggs or cocoons. They’re small amber or yellow, bead shaped eggs about 3 mm (1/8 in.) in size. Pick these out and return them to the worm farm.
You can use the 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, which can be used as a foliar spray on the leaves or watered into the soil.
What to Feed Your Worms
Things You Can Put In Your Worm Farm:
- Fruit peels and vegetable scraps
- Cooked vegetables, grains, pasta, and rice – but no meat-based sauces
- Coffee grounds and paper tea bags
- Egg shells
- Sea weed
- Scrap paper, newspapers, and napkins – do not use any glossy pages
- Soaked, unprinted cardboard
Things You Can Put In Your Worm Farm (with caution!):
- Vacuum cleaner dust – only if your carpets are made from natural (non-synthetic) fibers
- Citrus, onions, garlic & alliums – only in small amounts
- Bread and dairy products – no big chunks
- Weed seeds – they will end up in your compost
Things You Can’t Put In Your Worm Farm:
- Fish and meat – this attracts pests; use a separate bin for meat
- Fatty foods and oil
- Garden waste – put it into a compost bin, instead
- Glossy and bleached paper – this is toxic
- Fresh manures – vermicides will kill your worms
- Pet waste – only in a dedicated worm farm or compost bin
How to Feed Your Worms
When feeding, put the food on one side of the bed on top of the bedding, beneath the cover. Leave the other half uncovered to allow the worms space to move. Once the food on that side is eaten, add more to the other side, and alternate sides as you add more food.
When you first set up your worm farm, add a small amount of food, then add more a few days later. Don’t overfeed your worms, as the uneaten food will begin to rot and invite pests. As the worms multiply they will eat food faster, and you’ll be able to add more food. The worms double their population every 40 days, and will eventually self-regulate to match the size of the worm farm and the food available.
How to Separate Worms from Castings for Collection
The ‘Rainy Day technique’
If you have a worm farm with stacked trays, on rainy days the worms will rise to the top tray to avoid drowning. When this happens, the bottom tray will be filled with water. Empty it out via a tap on the bottom, or lift out the lower tray and gather the castings. With worm farms that have a door at the bottom to harvest castings, simply collect them and put them in a bucket.
The ‘Pyramid technique’
To separate the castings from the worms, gather your castings and place them in a pile on a low, flat container or board in a slightly shady spot outdoors, and mold it into a pyramid shape. Worms dislike sunlight, and they will burrow downwards to the base of the pyramid to escape the light at the top, leaving their castings behind. Wait a few minutes, scoop off the tip of the pyramid, and put it into a bucket. Then, reshape the pile into a new pyramid, moving the castings on the bottom to the top. Wait a few more minutes for the worms to dig down, and harvest the castings again.
The ‘Let The Worms Decide technique’
Worms have a preference for new bedding material with a fresh supply of food. Push the castings to one side of the worm farm to make a space, then put fresh bedding in that space, and lay down some new food on that side. The worms will move over to the area with fresh bedding and food, allowing you to collect their castings on the other side.
If you think your soil is too dry, use the squeeze test. Pick up a handful of castings and squeeze it in your fist. If just a few drops come out, this means it has the correct amount of moisture. If it’s too wet, then the system either needs better shielding from rain, or the drainage could be blocked. If it’s too dry, just add rainwater.
Some rainwater will eventually get into your farm. This flushes out the castings and makes a good supply of worm leachate. However, it can get over flooded. If your worm farm has a tap, leave the tap open and place a small bucket underneath to collect the leachate as it leaks out. You can save any worms from drowning if they fall into the liquid at the bottom by placing an upside-down terracotta pot on the bottom of the worm farm where the liquid collects. They will use this as an island to climb up to the top where it’s safe.
To prevent overheating, prop the lid open a bit to let out the hot air. You can also lay a stick across the top of the worm farm and place the lid over it to create a gap, allowing the air to circulate. On really hot days, water the surface with rainwater to cool it down. Make sure there’s a worm blanket over the bedding and food to keep the environment dark and moist. The best way to keep the farm cool is to cover it with a light-colored screen. A reflective plastic tarpaulin sheet, suspended above, also works nicely. Make sure it has sufficient air-space underneath so it doesn’t trap the hot air inside. Also, be sure to remove the cover when it’s cold.
Insects and Pests
Keep pests out by making sure the lid is secure. Ants may indicate the farm is either too dry, the food you’re using is too sugary, there’s too much food, or you’re not chopping it up enough. To discourage ants, dampen the worm farm with rainwater. To stop them completely, create an ‘ant moat’ by sitting the legs of your worm farm (if it has legs) in a tray of water. Smearing a band of Vaseline around the legs of the worm farm could also work, but may melt in hot climates.
Vinegar and fruit flies are attracted to rotting food, especially fruit. Prevent them from breeding by covering the food scraps with a damp newspaper. Other insects such as millipedes are not a problem, as they are also decomposers and will aid the worms in the process. Soldier fly larvae, which look like giant, silver-grey maggots, are also beneficial. Springtails, which are insects that hop around on the surface, are also friendly to this system.
If you see tiny white worms in your worm farm, these are entrachyadids. They are not harmful, but do indicate that your worm farm is probably too acidic. Correct this by sprinkling in a small amount of garden lime, crushed eggshells, dolomite, or wood ash every few weeks.
Smell & Odor
A healthy worm farm will have little to no smell, or smell of healthy soil or a forest floor. If it has a sharp vinegar smell, then it may be too acidic. If it smells quite offensive, or has started to putrefy, this is an indicator that the system has become anaerobic, and probably has too much nitrogen. To correct this, stop adding food, and balance the mix by adding materials high in carbon, like garden lime, dolomite or wood ash, and lightly stir up the existing food scraps to aerate it on a regular basis.
Mold is usually a sign that you are overfeeding the worms. Or, it can be because the worms are leaving some particular food for something they prefer to eat. To solve, just reduce the amount of food.