The most common problems with home worm bins are listed below. Remember that compost worms are living creatures. They need water, air, and food to live. They prefer a moist but not wet, non-acidic environment. Providing such an environment for your worms should prevent the following issues with your worm composting bin.
Foul Odor. Several related circumstances could cause foul odors.
(1) Check first to see if the bin is too wet. If the bedding is too wet, there will not be enough oxygen and the bin will become anaerobic. Condensation on the inside of the lid is normal. There should be no standing liquid in the bottom of the bin. The bedding should be damp, but not so moist that you could squeeze drops out of it. If the bedding is too wet, mix in some dry bedding and fluff up the bedding already there to introduce air into the bin. Make sure the ventilation holes have not become blocked, and consider adding more holes on the sides of bin.
(2) Check to see if there is a lot of food remaining in the bin, and if this seems to be the source of odor. You may have fed the worms more than they could eat in a few days. Add dry bedding to the bin, fluff and mix up what is there. Don’t give them more food until the worms eat what is currently in the bin. When you do resume feeding, cut back on the portions you are giving to them.
(3) Check if the odor is caused by a specific food. Your worms may not like that particular thing and would not eat it no matter how long it remains there. If this is the case, remove it and don’t put that type of food in the bin in the future.
Liquid Accumulating at Bottom of Bin. If liquid accumulates at the bottom of your bin, try reducing high-moisture foods from the worms’ diet and using drier bedding. If that doesn’t help, the climate you live in may be a factor.
This solution comes from the late Mary Appelhof: get a stocking or section of pantyhose, fill it with peat moss and tie off both ends with a rubber band, as if you were making a sausage. Set it around the bottom inside the bin, up against the walls. It will absorb the liquid. When the peat becomes saturated, empty the stocking’s contents for use directly in your garden or potting mix, refill stocking with new peat moss, and return it to the bin.
Worms on Inside of Bin Lid, Not in Bedding. This situation should be addressed as quickly as possible because it is an early sign that there is trouble. If the bin is not too wet (see above), then your bin may have become acidic. Remove any citrus, scraps that contain vinegar, and other acidic food. Mix in fresh bedding.
If the worms are not back down in the bedding in 24-48 hours, sprinkle a small amount of garden lime (calcium carbonate) in the bedding to help balance pH.
Worms Exiting Bin. If you have not been able to balance the pH in your bin, the worms will leave. At this point, to save your worms, you will need to make up a new environment for them to go to. You may want to pick worms out of the old bin by hand and add them to the new bin, otherwise they may not find it. See The Dreaded “Worm Crawl.”
Flies, Fruit Flies. The way to avoid all flies is to bury food wastes when you feed the worms. Flies lay eggs on exposed food, but they aren’t burrowers. They don’t have access to buried scraps for egg-laying.
If your bin has already attracted flies, do NOT put poison in the bin nor spray poisons around the bin. These will kill your worms. Look for a creative organic solution instead.
I tried getting a Venus Fly Trap plant once when my bin had fruit flies. That idea did not work fast enough. But I did finally get rid of them by putting some strong-smelling red wine in a mayonnaise jar, setting a funnel with a very small opening down into it, then taping them together where the funnel and mouth of the jar met. The flies could find their way in to get wine, but they (no doubt drunk) could not find the one tiny hole by which they could exit.
Centipedes. Centipedes kill earthworms. If you find one, you should remove it from the bin, watching that you don’t get nipped by its pinchers. (Millipedes won’t hurt your worms, leave them in the bin)
Earthworm Mites. A few earthworm mites aren’t going to cause problems in the bin ecosystem. But if their population starts to grow rapidly, place a piece of bread on top of the bedding. When they gather on the bread, remove it. Stop feeding for a few days until the mites are under control.
Ants in an Outside Bin. Add lots of water and they’ll leave. This may also reduce your worm population, but so would ants.
Other Critters in Bin. Other critters in your bin are probably beneficial to the ecosystem. You may see springtails, mold, fungi.
Human Allergies. If you are allergic to mold spores and fungi, consult your physician for advice and use your own judgment as to whether you can safely have a worm bin before establishing one. If so, keep your bin outside. Wear a protective mask when feeding or working with your bin.
Mary Tynes, Master Composter, www.mastercomposter.com
TOP LEFT IMAGE: 3-Tier Patriot Worm Tower with Tea Collector
BOTTOM RIGHT IMAGE: Worm Wigwam