Understanding what worms eat is fundamental to running a successful worm composting bin. Feed them the right things, and your worms will thrive, reproduce, and produce beautiful castings. Feed them the wrong things — or too much of anything — and you'll end up with a smelly, struggling bin.
At Wired Worm Farm, we've fed our worms just about everything you can imagine over the years. Here's the definitive guide to what composting worms eat, what they love, what they tolerate, and what you should absolutely keep out of the bin.
How Worms Actually Eat
First, a bit of biology. Worms don't eat food the way we think of eating. They don't have teeth. They don't chew.
Here's what actually happens:
- Microorganisms colonize food scraps. Bacteria, fungi, and other microbes begin breaking down the organic matter in your bin.
- Worms eat the microbe-covered material. Worms consume the softened, decomposing food along with the microorganisms themselves. The microbes are a significant part of the worm's nutrition.
- Food passes through the worm's gizzard, where it's ground up using tiny particles of sand, grit, and mineral matter.
- The worm's gut extracts nutrients and adds beneficial bacteria.
- Worm castings are excreted — the nutrient-rich, biologically active end product.
This is why fresh food sitting in a worm bin may go untouched for several days — the worms are waiting for microbes to do the initial work before they eat.
What Worms Love to Eat (The Best Worm Foods)
These are the foods that composting worms eat most readily and that cause the fewest problems in a worm bin:
Fruit scraps:
- Banana peels (cut into pieces for faster breakdown)
- Apple cores and peels
- Melon rinds (watermelon, cantaloupe, honeydew)
- Grapes
- Strawberry tops
- Pear scraps
- Mango peels
- Avocado flesh (not the pit or skin — these are very slow to break down)
Vegetable scraps:
- Lettuce and leafy greens
- Carrot peels
- Squash and zucchini
- Pumpkin
- Sweet potato
- Cucumber
- Corn cobs (break into pieces; they decompose slowly)
- Broccoli and cauliflower
- Bell peppers
Other excellent worm foods:
- Coffee grounds — worms love them; add filters too
- Tea bags — remove any staples; worms eat the tea and the paper bag
- Crushed eggshells — provides grit for digestion and calcium for reproduction; also buffers pH
- Plain bread and pasta — in small amounts, buried under bedding
- Rice — cooked or uncooked, in moderation
- Oatmeal — a worm favorite
- Shredded paper and cardboard — this counts as both food and bedding; worms eat the microbes that grow on it
What Worms Will Eat (With Caution)
These foods are acceptable but should be used in moderation or with specific precautions:
- Citrus fruits (oranges, lemons, limes, grapefruit) — Small amounts are fine. Large quantities can make the bin too acidic and repel worms. Cut into small pieces.
- Onion scraps — Worms tend to avoid raw onion, and it can create strong odors. Use sparingly.
- Garlic — Same as onions. Small amounts are okay; large amounts are problematic.
- Tomatoes — Fine in moderation, but they're very wet. Balance with dry bedding.
- Pineapple — Acidic. Small amounts only.
- Spicy peppers — Worms generally avoid capsaicin. Use very sparingly or not at all.
- Cooked vegetables — Usually fine, but avoid anything with heavy oils, butter, or salt.
What NOT to Feed Worms (The Worm Bin No-Go List)
These items should be kept out of your worm bin:
- ❌ Meat and fish — Rots quickly, creates terrible odors, attracts pests (rodents, flies, raccoons)
- ❌ Dairy products (cheese, milk, yogurt, butter) — Goes rancid, causes odor problems
- ❌ Oils, fats, and greasy foods — Coats bedding, reduces airflow, goes rancid
- ❌ Pet waste (dog, cat) — Contains harmful pathogens and parasites
- ❌ Glossy or coated paper — Contains chemicals and plastics
- ❌ Chemically treated wood or sawdust — Toxic to worms
- ❌ Plastic, metal, glass — Obviously not food
- ❌ Heavily salted foods — Salt draws moisture from worms through osmosis, potentially killing them
- ❌ Pesticide-treated produce — Residues can harm or kill worms; wash produce or buy organic
How Much to Feed Your Worms
The general rule of thumb: worms can eat approximately half their body weight in food per day under ideal conditions.
- 1 pound of worms ≈ 0.5 pounds of food per day (3.5 lbs per week)
- 2 pounds of worms ≈ 1 pound of food per day (7 lbs per week)
However, this is a guideline, not a rigid rule. Several factors affect how much worms eat:
- Temperature — worms eat more in warmer conditions, less in cold
- Bin maturity — a new bin with newly introduced worms eats less than an established bin
- Food preparation — chopped, frozen-and-thawed, or blended food is consumed faster than large chunks
- Microbial activity — food that's already starting to break down is eaten faster
Start slow. When your bin is new, begin with small feedings and increase gradually as the worm population grows and you observe how fast food is disappearing.
Tips for Feeding Your Worm Bin
- Chop food into smaller pieces. Smaller pieces decompose faster and are consumed more quickly.
- Freeze and thaw food scraps. Freezing breaks down cell walls, which accelerates decomposition when thawed.
- Bury food under the bedding. This discourages fruit flies and provides the dark, moist environment worms prefer.
- Rotate feeding locations. Alternate where you place food in the bin (left side, right side, center) to encourage worms to move throughout the bin and prevent any one area from becoming overloaded.
- Always add bedding when you feed. A handful of shredded cardboard or newspaper on top of each feeding maintains the carbon-nitrogen balance and controls moisture.
- Don't feed again until the previous food is mostly gone. This is the simplest way to prevent overfeeding.
The Carbon-to-Nitrogen Balance
A healthy worm bin needs a balance between:
- Nitrogen-rich materials (greens): food scraps, coffee grounds, fresh plant matter
- Carbon-rich materials (browns): shredded cardboard, newspaper, dried leaves, straw
The ideal ratio for a worm bin is approximately 3:1 carbon to nitrogen by volume (three parts brown to one part green).
Too much nitrogen (food) without enough carbon (bedding) leads to:
- Ammonia production
- Sour, acidic conditions
- Bad odors
- Worm stress
Always add a handful of shredded cardboard or newspaper when you feed. It's a simple habit that prevents most feeding-related problems.
What About Worm Chow or Commercial Worm Food?
Some worm farmers use commercial products like worm chow, chicken mash, or cornmeal as supplemental feeding — especially when raising worms for sale (vermiculture) and trying to maximize reproduction.
These products are fine as supplements, but for typical home vermicomposting, kitchen scraps and bedding provide everything your worms need. There's no requirement to buy special worm food.
Supplemental Feeding for Worm Reproduction
If you're focused on breeding worms (vermiculture), consider supplemental foods that boost worm reproduction:
- Cornmeal — a favorite among worm breeders for boosting population growth
- Chicken layer mash — provides protein and calcium
- Oatmeal — easy for worms to consume, promotes healthy growth
- Pumpkin — worms seem to reproduce more actively when pumpkin is part of their diet (many worm farmers swear by this)
Sprinkle a thin layer of cornmeal or oatmeal on the bedding surface once a week as a supplement to regular kitchen scrap feeding.
Signs of Correct Feeding
- Food disappears within 3–5 days
- Bin smells earthy and pleasant
- Worms are active and distributed throughout the bin
- Worm population is growing over time
- Castings are accumulating steadily
Signs of Feeding Problems
- Food sits unchanged for a week or more (overfeeding or too cold)
- Bin smells sour, rotten, or ammonia-like (overfeeding, too much nitrogen)
- Fruit flies swarming (food exposed on surface)
- Worms clustered away from food or trying to escape (pH too low, anaerobic conditions)
- Mold covering everything (overfeeding, too wet)
Final Thoughts
Feeding worms is simple once you understand the basics: stick to plant-based kitchen scraps, avoid meat and dairy, keep portions reasonable, and always balance food with bedding. Your worms will eat, multiply, and reward you with some of the finest natural fertilizer on earth.
At Wired Worm Farm, we're always happy to help you with feeding questions and worm bin management. Browse our worms and composting resources at wiredwormfarm.org.