Best Worm Composters: Indoor, Tray, and Flow-Through


Most gardeners are familiar with worm castings. They’re one of the best organic fertilizers and composts out there. You can generate your own castings using your kitchen scraps and a worm composter, also called a vermicomposter. But what is the best worm composter, and how do you choose with the wide variety that are out there?

Best Tray System: Worm Factory 360

Worm Factory 360 Worm Composting Bin + Bonus What Can Red Wigglers Eat? Infographic Refrigerator...
  • The Worm Factory 360 has a standard 4-Tray size which is...
  • The redesigned lid converts to a handy stand for trays while...
  • Includes digital instructional manual with step-by-step...
  • Bonus "What Can Red Wigglers Eat?" infographic refrigerator...
  • Built in "worm tea" collector tray and spigot for easy...

Other Good Options

How Does Worm Composting Work?

The simplest explanation of worm composting is one sentence: “Worms eat my kitchen scraps.” In essence, you provide a home for the worms (the composter), some lightly-moistened bedding, and food, and they give you fantastic compost.

Any fruit or vegetable scraps, leftover pastas or breads, leaves, coffee grounds, eggshells, and even some manures are great food sources for worms. Avoid feeding them meats or oils that tend to go rancid and smell bad. Adding large quantities of acidic foods all at once can actually irritate tender worm bodies and increase the pH of your bin, so go easy on acidic stuff. Avoid colored newspaper or cardboard, as some dye types can be dangerous or even toxic to your worms. And of course, never add inorganic materials like plastic or non-compostable materials like metal or glass, as the worms can’t eat those.

Eventually, it will be time to harvest your castings for use. Depending on the composter, this process will vary, so we’ll talk about that further on.

Common Problems And Questions

Q: My worm bin stinks! How can I fix it?

A: Your worm composter should not smell bad. Ideally, it will smell like garden soil, or perhaps whatever you’re feeding them if you’ve just fed your worms. If it starts to develop a bad odor, there’s probably too much food in there for your existing colony, and it’s starting to rot. If this happens, stop adding food until the worms have broken down what’s there.

If the worms still aren’t eating quickly, your waste may be too large for them to break it down quickly. Try finely-chopping your food waste to make it easier to eat. Some people even make worm smoothies by blending their kitchen waste into a pulp. You can easily freeze finely-chopped or blended worm food and give it to them as needed.

It’s also possible that you don’t have enough worms. 2,000 worms will break down about a pound of food waste per day. The worms do rapidly breed and can double their numbers in about 90 days, but a new colony is going to eat more slowly than an established one.

Q: How can I keep fruit flies out of my worm bin?

A: Fruit flies and other insects can show up when the food is too close to the surface and provides a tantalizing temptation. You can prevent this by lightly burying food scraps in the bedding an inch or two under the surface. You can also use a piece of damp cardboard or a few sheets of dampened newspaper on top to act as a block for other insects and to keep the bedding moist. And some bins have pest-prevention built in, like the Urban Worm Bag’s zippered top!

Q: Why are my worms trying to escape?

A: If worms are crawling up onto the sides and lid of your bin, there’s a few possibilities for why that’s happening. The bedding might have become too acidic. Reduce the quantity of citrus peels, pineapple scraps, etc that you’re putting in the bin. Adding some crushed-up dried eggshells can also reduce the pH level of the bin, which should make your worms happy.

It may also be too hot or cold in the bin – worms do best at temperatures between 60-80 degrees, so aim for that temperature range. And finally, it might be too wet or too dry. If you pick up a handful of the bedding and squeeze it, it shouldn’t drip but it should be moist to the touch. If it’s wet, you should drain off any liquid that’s accumulated.

Q: I have mold or sprouted seeds in my bin, is that bad?

A: Sprouted seeds aren’t a problem at all, just turn them under your worm bedding and the worms will feast on them. However, mold is another sign that your worms have too much food and it’s rotting before they can eat it all. You can prevent molds from forming by burying the food an inch or two under the bedding’s surface, and adding some moistened newspaper or cardboard over the top to help keep mold spores out. If you still get mold, whitish molds can usually be turned under the surface of the bedding and the worms will eat them, but black or green molds should be removed entirely and disposed of so they don’t spread.

What Else Do You Need To Start?

You’ve chosen a worm composter. What else do you need to start vermicomposting?

Well, live composting worms, of course. The best composting worms are red wigglers or European nightcrawlers, both of which are available for purchase. Common worm species used for the purpose include Eisenia fetida, Eisenia hortensis, and Perionyx excavatus. Unfortunately, the earthworms that are common in many areas just don’t eat enough, so they aren’t as useful in your colony. 2000 worms will eat about 1 pound of food every 24 hours, so make sure you get enough for your bin and waste production levels.

You also need bedding for the worms to live in. My personal favorite is coconut coir. I prefer either moistened coco pith/peat or maybe a fine coco fiber, as coco chips don’t provide a soil-like environment. However, you can also use finely shredded newspaper or cardboard that’s been lightly dampened. I recommend adding a couple scoops of garden soil and mixing it into the bedding as this provides the grit worms need to digest their food. They can also use coffee grounds, rock dust, or powdered eggshells as added grit sources. I also advise burying a few larger fragments of eggshell or corrugated cardboard in the coir, as worms like to breed and lay eggs in the shelter these provide.

It might be useful for you to pick up a worm farm thermometer as well. It’s not required, but if you have wildly fluctuating temperatures, it helps. Red wigglers like between 60-80 degrees Fahrenheit, and if it’s too hot or cold they don’t do as well!

What To Look For In A Worm Composter

While you can DIY a worm composter out of almost any box or bucket, there’s a few things which rudimentary types lack that are available in commercial vermicomposters.

Drainage. If you’re adding a lot of fruit or vegetable matter, especially stuff like watermelon rinds or other wet materials, it will produce a liquid that’s referred to as “worm tea” or leachate. Your worms don’t want the extra moisture and can actually drown if there’s too much, so a spigot or other draining method for leachate is required.

Incidentally, the leachate itself does contain some nutrients and can be used as a fertilizer source, but with one caveat: As it doesn’t go through the worm’s gut and get digested, it may have pathogens that haven’t been eradicated, so it’s not safe for use on edible plants. If your vermicomposter has a spigot, you can drain off the leachate regularly, mix it at least 50/50 with water, and spread it on your lawn or on the soil in a flower garden. It can also be added to a hot compost pile, as the heat will kill any pathogens in the leachate.

Ease of Harvesting Castings. You can make a composter out of a bucket with holes drilled in it for drainage… but you’ll have to pull out all of the worms, their remaining bedding/food, and their castings and manually separate them all. Most commercial composters provide alternatives which don’t disturb your colony. The less you disturb your colony, the quicker they will reproduce and make you great castings, so a built-in option that makes the process easy is ideal.

Composting Space. If only one person is producing waste food for the worms, you probably don’t need a very big composter, nor a whole lot of worms. But what if your family grows and you start producing a lot more compostable waste? Ideally, you’ll want a composter that can expand with your needs, allowing your worm colony to breed and expand as well.

Shade. Worms naturally live well away from sunlight, so you want your composter to simulate that natural environment as much as you can. Choose a composter that’s opaque so that it can block excess light.

Ventilation. Composting worms need to breathe just like we do. Ensuring that they have a well-ventilated composter is a must.

Protection From the Elements. If you plan on putting your composter outside, you need a lid to keep rain out, and you need to place it in a shady area so it doesn’t get overheated in the sun. If you’re putting it indoors, you can opt for a different setup, but you will need to make sure it’s still somewhat climate-controlled.

Best Worm Composters

Let’s take a detailed look at some of the best worm composters on the market and see how they work.

Best Overall Worm Composter: Worm Factory 360

Worm Factory 360 Worm Composting Bin + Bonus What Can Red Wigglers Eat? Infographic Refrigerator...
  • The Worm Factory 360 has a standard 4-Tray size which is...
  • The redesigned lid converts to a handy stand for trays while...
  • Includes digital instructional manual with step-by-step...
  • Bonus "What Can Red Wigglers Eat?" infographic refrigerator...
  • Built in "worm tea" collector tray and spigot for easy...

The Worm Factory 360 is the easiest system to use. It arrives out of the box with four trays, a lid, and a base with a built in leachate collector and spigot. To use it, just add your bedding and your worms, then feed. As you slowly fill up trays, you gradually add more trays with bedding and food on top. The worms easily slip through the holes in the bottom of each tray, working upward to the freshest food source.

By the time you fill the fourth tray, all of the worms should have finished eating the bottom tray and have worked their way up, and the bottom is ready to harvest. The lid acts as a handy stand for the other trays while you’re removing the bottom tray. The leachate collector base keeps excess moisture away from your worms and allows for easy drainage.

It’s expandable up to eight trays, which means you don’t have to rush to harvest your finished compost and can store it right in the Worm Factory.

See Prices >

Best Value Worm Composter: VermiHut 5-Tray

VermiHut 5-Tray Worm Compost Bin, Dark Green with Free Worm-saver Tray
  • Better air-flow control, high compost efficiency, small...

This composter is also a tray system, so it works very similarly to the Worm Factory 360. However, it’s a 5-tray system and extra trays aren’t available, so you’ll need to harvest the lower trays as they are finished rather than storing compost under the colony. It also has a built-in spigot and leachate collecting basin, and the angled lid provides a little extra rain-shedding capability for outdoor use.

Overall, this is a great unit for people who’re just starting out and who can use their castings year-round rather than store them.

See Prices >

Best High-End Composter: Hungry Bin Composter

Worm Farm Compost Bin - Continuous Flow Through Vermi Composter for Worm Castings, Worm Tea Maker,...
  • EASY TO USE: The Hungry Bin is a continuous flow-through...
  • MULTI-USE: Not only can you make the highest quality worm...
  • FAST AND CLEAN: Hungry Bin processes up to 4.4 lbs. (2 kgs)...
  • ECO-FRIENDLY: You will be saving food scraps from going into...
  • LIFETIME GUARANTEE: Hungry Bin has been designed to last,...

The Hungry Bin is a flow-through system rather than a tray system. When it arrives, you set it up, place the leachate catch-tray underneath, and add your bedding and worms at the bottom, then gradually add food on top. As the worms eat, the castings fall down to the bottom of the composter, creating a layer of ready-to-use castings. When you’re ready to harvest, just follow the instructions on how to open the base and scoop out your finished compost.

It does have a sizeable price tag, but flow-through systems like this eliminate the need for stacking up excess trays elsewhere, and it provides year-round compost in a small footprint.

See Prices >

Best Indoor Composter: Urbalive Composter

Urbalive Indoor Worm Farm - Organic Compost Vermicomposter, Chic European Design (Anthracite)
  • Smart kitchen bio waste processing.
  • Indoor year-round use.
  • Sleek & modern European design and origin.
  • Step-by-step instruction guide.
  • Great tool for ecological education.

Do you want a small system that looks good in your house? In that case, the Urbalive is your best bet. It’s a 2-tray system with a leachate collection base, so it doesn’t have as much capacity as other varieties, but it has a streamlined look that easily fits into your home decor.

It’s slightly pricier than other tray systems, but definitely more visually-appealing than any other tray system out there. You can bring most bin types inside, mind you! But this one is meant to be indoors as a feature.

See Prices >

Best Flow-Through Worm Bin

Urban Worm Bag
The 2.0 version of the Urban Worm Bag improves on a few key features.

Flow-through systems are all the rage for those who aren’t a fan of stackable systems like the Worm Factory 360. This one in particular is made with 900 denier Oxford fabric, meaning it’s breathable but won’t allow in any flies, etc… a common problem in other systems.

It’s capable of holding up to 5 cubic feet of vermicompost, but most importantly has an easy-harvest zippered bottom that makes getting fresh castings out of the system an absolute breeze.

See Prices >

Other Good Options

Redmon Green Culture 65-Gallon Compost Bin

Redmon Green Culture 65-Gallon Compost Bin
  • Rugged, weather-resistant plastic resin
  • 65 gallons 8.6 cubic feet
  • Convenient lift-off lid for easy access
  • Ventilation holes for proper composting
  • 4 door access

If you are looking for the easiest solution possible and want your vermicomposter outdoors, this bin can work. This is a traditional compost bin that can handle a huge quantity of kitchen waste, leaves, trimmings, and other compostable materials with ease, and since it lacks a bottom and sits directly on the soil, any leachate drains out into the ground.

Most people forget that worms can live inside a traditional compost unit like this, too! If you add fresh food for them regularly, the worms you’ve added will stay in and under your bin and continue to rapidly break down your waste into castings.

However, if you stop feeding more appealing kitchen scraps with regularity, they may start digging down into your soil and going in search of other food, so you have to make sure you’re feeding regularly.

See Prices >

The Worm Inn

The Worm Inn (Green) - The Worm Composting Solution! Discover AIR FLOW Composting! Best Worm...
  • The Worm Inn is the most breathable worm composting system...
  • Manufactured using extraordinarily durable Cordura Diner....
  • A true flow thru processor. Unzip the mesh screened top to...
  • No more time consuming harvests. Collecting your...
  • The Worm Inn makes worm composting simple and enjoyable!

Are you curious about flow-through vermicomposters, but don’t want to lay out the high price for the Hungry Bin? Then this is your option. The Worm Inn is a flow-through bag system. When suspended from a frame, a leachate tray can be placed underneath and it works very similarly to the Hungry Bin in design. As it’s a heavy-duty mesh fabric, it’s well-aerated and drains leachate easily

Instead of a lid, a mesh flap with a zipper is attached, allowing you easy access to add more compostable materials. However, this system must be used indoors, either in a garage or other covered environment, as it has no protection from sun or rain.

See Prices >

In Summary

Overall, the best unit for most people to look into, whether they’re a newcomer to vermicomposting or a pro, is the Worm Factory 360. It provides the most composting capability in a small space with lots of expansion potential, is opaque to block out light, well-aerated, protected from the elements, and is easy to harvest from. But whether you start with that or any other system, worm composting is a great way to produce high-quality compost for your plants, and I hope you give it a try!

The Green Thumbs Behind This Article:

Kevin Espiritu

Lorin Nielsen
Lifetime Gardener

Did this article help you? Yes No
× How can we improve it?
× Thanks for your feedback!

We're always looking to improve our articles to help you become an even better gardener.

While you're here, why not follow us on Facebook and YouTube? Facebook YouTube

Last update on 2019-09-17 / Affiliate links / Images from Amazon Product Advertising API

Leave a Comment