How to Make a Composting Worm Bin Plus Key Worm Bin Facts


In 2018 about 35.3 million tons of food went to landfills in the U.S. Worm bins can help to reduce this figure, as they convert kitchen scraps into beneficial compost for gardening. You can get worm bins in stores and online, but they’re also easy to make right at home. 

To make a composting bin, you will need three plastic totes with holes drilled in the bottom and sides of two. The bottom holes allow the worms to migrate upwards to the other bins, while the holes on the side provide aeration. Stack the three totes with the one without holes at the bottom.

This article provides a detailed guide on making a worm bin for composting at home, the right worms to use, and the proper way to maintain the worm farm for optimum productivity. The article also provides a guide for farming worms in bathtubs as an alternative method.

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Photo of a green worm composter in the garden with a worm tea sprout
Photo by Hollyharryoz

How do Worm Bins Work?

Worm bins are used to convert organic materials into compost for gardening and farming by housing several worms and providing a steady supply of organic waste, usually kitchen scraps like vegetables, fruits, coffee grounds, bread, and cereal. The worms eat the scraps, digesting and passing them out as compost and a dark liquid called worm tea, both of which are very beneficial for plants.

Worm bins can be constructed with three or more bins or trays with holes in the bottom, stacked to create levels. However, you can’t simply fill some old bins with the earthworms you find in your garden.

These bins house a particular kind of worm known as red wiggler, redworm, tiger worm, or Eisenia fetida if you enjoy scientific names. These worms, unlike regular earthworms, don’t dig down but migrate upwards to the food source, leaving their castings (the compost) behind.

Initially, the worms are placed in the second to last tray, along with some food scraps. They will eat the food, turning it to compost, and when there’s no more food left, they will migrate through the holes to the next tray/bin above in search of more food, leaving the castings behind.

When there’s no more food, the tray is removed, and the compost harvested for use in the garden. The now-empty bin is rotated to the top, where it will eventually house the worms again.

By taking advantage of the worms’ desire to climb and continuously rotating the trays to the top, worm bins provide a more manageable and space-saving method of vermiculture.

Making a Worm Farm in a Bin

Worm bins are simple to use and just as simple to make. You will need the following tools and materials to begin:

  • Drill:  A drill with 1-1/8 inch (28.58 mm) diameter drill bits to make holes in the bottom and sides of the buckets.
  • Trowel: A trowel to harvest the compost.
  • Plastic tubs: Three 10-gallon plastic totes or buckets with lids. Choose ones with slightly tapered sides, so that they do not sit fully inside each other, providing some space for the worms and their castings.
  • Soil: Garden soil is essential for the worms’ survival and provides some grit to help worms “chew” the food.
  • Screens: A screening material to cover the side holes and prevent the worms from escaping. It’s best to avoid metal, as these will rust over time, so choose vinyl screens instead.
  • Glue:  Waterproof glue to attach the screen to the buckets
  • Shredded paper or cardboard: This serves as bedding for the worms. Avoid shiny or colored papers, as the ink in these can harm the worms.
  • Worms: A pound of red wiggler worms.
  • Plug (optional but recommended):  A cooler drain plug to drain out excess liquid that accumulates.

When you’ve gathered all of these, follow the steps below to make your worm bin.

Put Markings on the Containers

Stack two of the three containers and use a ruler or tape to measure how much of the top container sticks out from the second. Whatever you get is roughly equal to the amount of space between the two containers when you stack them. This space is where the worms and the compost will reside.

Jalape_o_Pepper_Lines (4) x
Jalape_o_Pepper_Lines (4)

Next, put your tape inside the container till it touches the base, then measure upward. Make a mark at a point that’s one inch (25.4 mm) less than the measurement you got the first time.

So, if you got six inches (152.4 mm) when you measured the portion of the tote that stuck out, you’ll measure five inches this time and mark the point with a straight line. The line you just made will serve as a guide to tell you when it’s time to stop feeding the worms and harvest the compost.

Drill Holes in the Bottom of the Containers with Markings

Use the larger drill bit to make holes in the bottom of the two containers you drew lines on. Make as many holes as possible and ensure they’re evenly spaced at an inch (25.4 mm) away from each other. Do not drill holes in the last container; otherwise, you’ll have a mess on your hands.

Drill Holes in the Sides of the Containers

Drill a line of smaller holes on the sides of the two totes with bottom holes. Like before, position the holes one inch apart.

These new holes should be near the top of the container and will supply air to the worms within and prevent things from getting too wet inside.

Drill Holes into the Lid of the Container

Use the same drill bit used for the sides to drill several holes into one of the containers’ lids. These new holes will provide even more aeration to the bin, speeding up the breakdown of the contents. Aeration is vital to the composting process, and without it, you will likely smother your worms.

Install a Cooler Drain Plug on the Third Container

This step is optional. The third container serves as a sump to collect the leachate (excess liquid) from the worms above. The drain plug isn’t essential, as you can turn out any liquid that collects inside. However, installing a drain plug will save you a lot of trouble, as you can simply open it up and allow the liquid to flow out. This means you don’t need to dismantle your bins to turn out the water manually.

If you decide to have a drain plug, we recommend the Coleman Cooler Standard Drain Assembly, which can be found on Amazon by clicking the link. It’s quite affordable and has a drain spout and a gasket to prevent leaks.

Attach the Screens to Cover the Side Holes

Apply glue to the sides of the container, a few inches above and below the line of holes you made, then place the screen and press down on it so it bonds well. Make sure the glue is completely dry before proceeding to the next step. If the glue is not dry, it will become wet and come away over time.

Assemble the Worm Bin

Assemble the worm bin by putting one of the containers with holes into the one without holes. The hole-less container will serve as the base of the worm bin to collect any liquid from the worms above and should be placed on some bricks or cinder blocks to allow enough space to open the drain plug and collect the juice.

It’s also important that you choose a shady location for your worm farm, as worms don’t like much sun. A corner in a shed or garage will do nicely.

Add Shredded Paper and Soil for Bedding

Make the bedding by combining shredded paper with a few handfuls of potting soil. Like chickens, worms have no teeth and rely on the grit in the soil to help them break down the food and a little water to make it damp. Put the mixture into the stacked containers and ensure that it rises to at least three inches.

Transfer the Worms to the Container

Transfer the worms into the container along with whatever bedding they came with. It’s okay to add some food scraps at this time, but best to wait for 24 hours to give the worms time to acclimatize to their new home before feeding them.

Meanwhile, cover the worms with a worm blanket of cardboard, hessian sack, or old towels, then put the lid over the container.

Feed the Worms

After 24 hours, lift the blanket, and put some food scraps into the container covering it in beddings. Replace the lid and allow the worms to do their thing. You can add more food as often as you want, but ensure you always cover the food, as exposed food will attract fruit flies.

Sprinkle some water periodically to keep things moist (but not wet), especially if the food isn’t producing much moisture. But if you’re using mainly wet foods like fruits, and vegetables, you may not need to sprinkle water frequently or even at all.

Add the Third Container

After a few weeks, the worms will multiply, and the castings will increase considerably. Stop adding food scraps when the compost reaches the line you made on the container. Instead, add the third container, along with beddings and food. The worms will migrate up into the new bin within the next couple of days.

Harvest the Compost

When all the worms have moved to the new bin, it’s time to harvest the compost they leave behind. To do this, lift the top bin, which now houses the worms, and set it on the ground. It’s best to put a layer of cardboard between the container and the bare ground to prevent any crawling insects from getting into the bin through the holes.  

Bring down the second container (the one with compost) and scoop out the compost with a trowel. But be careful, there may be a few worms still inside, and you don’t want to hurt them. If you find any worms, remove them and put them back in with the others.

The sump should be exposed at this time, so you can see if there’s any liquid inside. If you’ve installed a drain plug, simply open it and collect the liquid in a bowl. If you don’t have a drain plug, then you’ll need to lift the container and pour out the contents.

The compost and leachate (also called worm tea) are excellent soil materials that you can use for virtually all plants.

Repeat the Process

After harvesting the compost and leachate, return the bin housing the worms. But place it over the sump this time, where the previous container used to be.

As long as you keep feeding the worms, the compost will accumulate again. When the compost rises to the mark you made on the container, repeat the above steps by rotating the top two bins.

Making a Worm Farm in an Old Bathtub

Did you know you can repurpose an old bathtub into a worm farm? A bathtub worm farm is easy to set up; here’s what you’ll need.

  • An old bathtub.
  • Shade cloth or synthetic landscape fabric large enough to cover the floor and sides of the bathtub.
  • Six cinder blocks or concrete blocks.
  • Some coarse gravel.
  • Shredded paper or cardboard that is neither glossy nor brightly colored, as the ink can be toxic to the worms.
  • Some garden soil.
  • Two pounds of red wigglers.
  • Plywood, planks of wood, or a tarp to cover the bathtub after the bin has been assembled

When you have all the materials and tools ready, follow the steps below to set up the bathtub worm farm.

Choose a Suitable Location

Choose a suitable location for your bathtub worm farm. It should have enough shade, and the ground should be level so that the tub balances well. Ideally, you will want it away from the house and out of sight. A garden shed or greenhouse would be ideal as it will protect the farm from the elements.

Use Cinder Blocks to Elevate the Bathtub

Place the tub on level ground and arrange the blocks beside it, one at the end, middle, and right before the drain.

Make sure it’s the short side of the blocks and not the long side that touches the tub. And if you’re using hollow blocks, ensure that the holes face upwards, not sideways. Finally, add one more block on each of the previous ones to increase the height, then lift the bathtub onto the blocks.

Raising the tub off the ground is essential for airflow under, around, and through the tub, via the drain. Without proper aeration, the food scraps will decay slowly and anaerobically (without oxygen), which isn’t good for the worms.

Another reason to lift the tub is for easy drainage and collection of worm juice. If the bathtub is left on the ground, the leachate will remain in the tub, making the tub soggy and smelly.

Put a Screen Over the Drain

Drains allow air and the worm juice to pass, but they will also let the gravel fall out and critters get in.

Depending on the bathtub, there may or may not be a drain strainer in place. If your tub doesn’t have one, you can get one. We recommend getting the Maxware Stainless Steel Bathroom Strainer available on Amazon. Each pack contains four different sizes, and one is sure to fit your tub.

Put Some Gravel in the Tub

With the drain strainer in place, it’s time to add the gravel. The main purpose of the gravel is to provide drainage for the worm juice.  

When you put the gravel into the tub, ensure that there isn’t a slope. Bathtubs usually have a sloping floor, deeper at the drain end, so to correct this, you’ll need to put more gravel at the deeper end; this way, you’ll obtain a level bed for the worm farm.

Line the Tub with Shade Cloth or Landscape Fabric

Cover the gravel and sides of the tub with either shade cloth or synthetic landscape fabric. This lining acts as a sieve, allowing the worm juice to pass but retaining the worms and the compost.

If you choose shade cloth, use one with a high shading percentage, like 80 and above. These types have smaller holes, so even tiny worms can’t escape through.

Make the Bedding

To make the bedding, put a lot of shredded paper (up to three inches thick) into the tub, then add some garden soil, compost, and water to make things moist. Be sure to add the water slowly, as too much will oversaturate the mix, and the worms won’t be able to survive.

Transfer the Worms

Transfer the worms into the bathtub with whatever bedding they came with. Don’t add food scraps at this time but wait for 24 hours to give the worms time to get used to their new home before feeding them.

Meanwhile, cover the worms with a worm blanket of wet hessian sack, wet cardboard, or old wet towels.

Cover the Tub

A worm blanket isn’t enough protection from sunlight, animals, and insects, so you’ll need to cover the bathtub, too. You can use old roofing panels, a piece of plywood, or several planks laid side by side to cover the tub. Alternatively, you can use a tarp or large piece of cloth.

Feed the Worms

After a day or so, lift the blanket and put some food scraps into the bin. Don’t add too much, as you will overwhelm the worms, and that will inhibit their progress. Instead, scatter the food over the top evenly and keep an eye on it until you get a good idea of how fast they work. Replace the blanket and lid, and let the worms get to work.

Harvest the Compost

As long as you keep feeding the worms, the compost will accumulate, and you’ll eventually want to harvest it for use in your garden. When you feel it’s time to harvest the compost, stop spreading the food out evenly over the top and, instead, put all of the food to one side of the tub. This will cause the worms to migrate to where the food is, leaving behind their castings.

It may take up to ten days or more for all the worms to move, but you can harvest the entire compost on that side when they do.

After harvesting, put some shredded paper on the empty side of the bathtub. Moisten the paper, then level the compost on the other side so it covers the shredded paper. You can then resume feeding the worms like before.

The next time you want to harvest the compost, repeat the process but on the other side, alternating sides each time you harvest. 

Photo of a grey plastic worm composter, with its lid open, filled with kitchen scraps
Photo by Ashley Belle Burns

Best Premade Worm Composting Bins

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If you’d rather not make a worm farm yourself, you can buy one online and in stores. There are many options available in the market, but here are three great options for you.

Highest Quality: Worm Factory 360 Worm Bin

The Worm Factory 360 comes with four trays and a base with a spigot to collect the worm tea from the system. The lid can be converted to a stand for the other trays when you want to harvest compost from the bottom tray.

Besides the four trays that come in the box, the worm bin is expandable to eight trays, making it one of the largest available. You get some bedding materials and an accessory kit with tools like a thermometer, hand rake, and scraper to make managing the worm farm easier. The Worm Factory 360 is available in black, terracotta, and green colors.  

Pros

  • It has a spigot so you can easily get out the worm tea.
  • The convertible lid holds trays when harvesting compost, so they do not rest on the ground.
  • Expandable to eight trays, which helps store compost.
  • Bedding and accessory kit included.

Best Value: Vermihut 5-Tray Worm Compost Bin

The Vermihut 5-Tray Worm Compost bin is quite similar to the Worm Factory 360, with a base fitted with a spigot for leachate draining. It has five trays made from recycled plastics, but unlike the Worm Factory 360, it isn’t expandable and doesn’t have a convertible lid. However, the lid has holes in the sides for proper aeration.

Pros

  • Leachate collecting basin with a spigot for easy worm tea retrieval.
  • Ventilation holes keep the worms healthy and prevent foul odors.

Most Affordable: Teemway 4-Tray Worm Bin

As the name suggests, the Teemway 4-Tray Worm Bin has four trays, yet it still manages to be compact, measuring 9 x 8 inches and standing at about 12 inches when all four trays are used.

The trays are plastic, and one is see-through, while the others are green. There’s a smaller plastic sump with a spigot at the base to collect leachate from the system, and all of these rest on a metal stand.

Pros

  • It’s fitted with a spigot so you can easily get out the worm tea.
  • Compact size, so it can fit under the kitchen sink.

Feeding Compost Worms

Worms aren’t picky eaters and will eat fruits, leafy greens, coffee grounds, bread, and cereal. They can also eat woody or dry items like stems and the outer layers of an onion, but it will take longer since they are tougher and drier.

Citrus, like orange, lime, and lemon, are somewhat acidic, so do not put too much of these into the worm farm (not more than 20 percent of the total food), and when you do, try to cut them up into bits.

Cow, horse, and goat manure are also good for compost worms since these animals eat a strictly plant-based diet.

Foods That Shouldn’t Go into Your Worm Farm

Contrary to popular belief, worms aren’t vegetarians and they’ll eat anything from a living organism. However, not all organic foods are meant for a worm bin, and you should avoid feeding your worms:

  • Meat and other animal by-products like dairy, fat, eggs, and bone 
  • Dog and cat feces since they eat meat and other animal products

These foods take longer periods for the worms to process, and in that time, they can cause foul smells and attract undesirable vermin, like rats or mice.

Photo of a lady showing off her red worm composter to others. She is takin the composts temperature to make sure it isn't too hot
Photo by Leosanches

Worm Bin Frequently Asked Questions

  • How deep should your worm bin be? Worm bins should be between eight and twelve inches deep (203.2 – 304.8 mms), as tiger worms feed at the surface, and too deep a container may cause odors.
  • How many worms do you need to start a worm bin? Depending on the size of the bins, you can start a worm bin with a pound of red wigglers which typically amounts to about 1,000 adult red worms.
  • What types of worms should you get for your bin? Red wigglers (Eisenia fetida) are the best worms for worm bins, as they’re surface dwellers and better suited to life in a worm bin.
  • Where to buy worms for a worm bin? You can buy worms in bait shops, lawn and garden catalogs, and online too.
  • How long will my worms live? Tiger worms live for about one year in a worm bin. When they die, they decompose and become part of the compost.
  • What is a worm blanket? A worm blanket is a material placed over the food scraps and worms to provide the dark and moist conditions worms enjoy. Worm blankets are sold in stores, and you can also use a hessian sack, cardboard, or old towels. 
  • Do worms like warm or cold soil? Worms like neither warm nor cold soil. They do best in temperatures around 57 to 60 degrees Fahrenheit (13.5 to 15.5 degrees Celsius).
  • Should you keep a worm bin inside or outside? You can keep worm bins inside your home or outside; only ensure that the place is well ventilated and shaded (if outside).
  • Is mold okay in worm bins? Mold doesn’t affect the worms; they’ll eventually consume it like other food scraps.
  • Do worm bins need air holes? Yes, worm bins need air holes. Without fresh air, the food scraps will decay anaerobically, which isn’t good for the worms.
  • Why does my worm bin smell? A smelly worm bin might be because of a lack of ventilation, too much water, or too much decaying food.
  • How to keep ants out of my worm bin? Put the legs of the bin in trays of water.
  • Why are my worms dying? Your worms could be dying because of a lack of ventilation, not enough or the wrong food, too much water, or even if it’s too cold or too hot.
  • How long does it take for worms to reproduce and multiply? It takes between two to three weeks for mature worms to mate and reproduce.
  • How long does it take to make compost with worms? Depending on the number of worms, it can take between three to six months to get a reasonable amount of compost.
  • How do you use your worm compost? With potted plants, you can simply spread it over the top layer or mix it in with garden soil when repotting. In the garden, work the compost into the soil around the base of each plant.
  • Can you have a worm bin in an apartment? Sure, worm bins can stay in an apartment; just ensure that you place them in a cool and well-ventilated area so that there won’t be any smells. Always make sure to check your lease or other agreements to ensure this is allowed in your building before you keep one.
  • How often should you feed your worm bin? Depending on the number of worms, you can feed them weekly or every other day. A foul smell is an indication of overfeeding.
  • Should you stir your worm bin? You don’t need to stir a well-designed worm bin with proper ventilation and drainage. Additionally, the worms themselves aerate the compost as they move around in the bin.
  • Why are my worms crawling out of the bin? Worms crawling out of the bin are likely trying to escape from the heat in the bin, excess moisture, insufficient ventilation, or overcrowding.
  • How do you know if your worms are happy? If your worms aren’t trying to escape from the bin, then they’re happy.
  • Why are my worms skinny? If your worms are skinny, then it’s because of a lack of food, moisture, or overcrowding.  

Closing Thoughts

Worm bins are great and effective ways to turn waste into helpful soil conditioners for use in the garden. You can make a worm bin yourself using plastic totes, a drain plug, vinyl screens, and a drill to make holes. Feed your worms vegetables, coffee grounds, cereal, bread, fruit, and manure from herbivores, and never give the worms animal products like meat, dairy, and bones as these take longer to break down, cause odors, and invite vermin to the worm farm.

Supriya

Hi! I'm Supriya. I'm a home cook, bulldog mom, spicy food lover, and founder of The Spicy Trio. I have been a home cook for about 15 years and have been growing plants for the past six years.

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