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Troubleshooting Indoor Worm Bin Composting


Taking steps to avoid problems with your worm bin is often easier than getting rid of problems once they've started, so it's important to monitor your bin regularly for the problems below.

If a problem develops that cannot be controlled, the best solution may be to harvest the worms and start a new bin from scratch, using what you have learned from your past experience to create a better bin.

Call the compost helpline number at the NYC Compost Project nearest you for help with these and other problems.

odor problems and solutions
fruit flies problems and solutions
worm death problems and solutions

setting up your worm bin
adding worms to your worm bin
adding food scraps to your worm bin
harvesting vermicompost
outdoor composting
other ways to recycle food scraps

illustration: broccoliOdor Problems and Solutions

Exposed food. Cover food scraps with bedding.
Too much moisture. Add dry bedding so that it can soak up pooling water, particularly in wet areas. Reduce the amount of food placed in the bin.
Not enough oxygen. Add dry bedding; fluff up the bedding if it appears matted down.
Too much food; not decomposing. Break food into smaller pieces, especially hard, woody items like stems; freeze and thaw to break down cell walls. Feed worms less so that they have time to go through food in the bin.

Food in bin is naturally odorous. Some foods are naturally odorous when decomposing (such as onions, broccoli, or cabbage, plants in the allium or brassica family). Therefore, remove foods that produce unpleasant odors if it bothers you. Don’t add meat, bones, dairy, or oil products, as these turn rancid.
Dead Worms. See Worm Death section below. 

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illustration: funnel fly trapFruit Flies Problems and Solutions
If fruit flies are a problem, you can try using flypaper traps or make your own fruit fly trap. To make a Funnel fly trap, simply pour some apple cider or beer into a glass jar and add a drop of detergent. Cut the corner off a plastic sandwich bag and place it into the jar; secure the plastic-bag "funnel" with a rubber band around the rim of the jar. illustration: bottle fly trap

To make a bottle fly trap, cut a small plastic water or soda bottle in half. Fill the bottom half with some apple cider or beer and a drop of detergent. Turn the top half upside down and place it into the bottom half so that the neck forms a funnel. Secure the two halves with tape.

House flies should not be attracted to your worm bin if you cover the food scraps with bedding material.
Exposed food. Bury food under bedding material; cover the contents with a dry sheet of newspaper.
Too much moisture.  Avoid overfeeding; add dry bedding.
Fruit fly eggs in food scraps. Cut fruit into small pieces; wash all fruits and peels, particularly bananas and citrus. Freeze fruit before feeding to worms or microwave fruit for 60 seconds. These actions help to kill fruit fly eggs. You can also simply avoid adding fruit. 

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illustration: hand forkWorm Death Problems and Solutions

Dead worms decompose rather quickly; you can have a bin with no worms before you realize it.
Bin is too wet; worms are drowning. Add dry bedding; leave lid off for an hour or two to allow water to evaporate. Make sure bin is well ventilated.
Bin is too dry; worms are drying out.  Lightly moisten and turn bedding; add moist foods. Make sure it’s not too hot for the worms.
Not enough air; bedding and food are matted together; worms are suffocating. Fluff bin contents to aerate. Be sure bin is adequately ventilated with holes; add paper tubes or other bulky paper products such as torn up paper egg cartons to increase air flow.
Not enough food. Increase food, or reduce number of worms.
Worms not eating. Avoid adding too much food at one time. Avoid very spice foods, salty foods, large amounts of citrus, or toxic ingredients like alcohol.

Bin is too hot or too cold.  Worms prefer the same temperatures that people do, so it’s best to keep the bin in a location where the surrounding temperature is between 55°F and 80°F (13°C and 27°C). Smaller bins are more impacted by surrounding temperatures so keep these in a location with temperature controls.
An over-abundance of mites. (A small mite population is natural, but if you notice large collections of mites, you should try to remove them.) Remove any food that has a congregation of mites. To reduce mites, bring bin outside and leave it open in the sun for 1–2 hours to dry it out a little. Repeat as necessary until mite population is reduced. To trap mites, place a slice of fresh bread in the bin, wait until mites congregate on it, and then remove the bread.

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