Feeding worms

Once the worms are established in their home, it’s time to feed them.

What do worms eat?

As I understand it, worms don’t actually break down the food waste directly; they eat the microorganisms who do. To be honest, I don’t really understand the advantages of this system over a conventional composting system. Does the worm bin ecology control the microbial population so that you have the right kinds and the right numbers? Do the worms provide extra aeration with all their wriggling? Perhaps the biggest advantage is simply that vermicast, or worm poop, is more nutritious for plants than regular compost.

Anyway, because worms eat decomposers, we let our food waste ‘age’ and decompose a bit before we put it in the worm bin. That way, the food waste has already developed a good population of microorganisms that are worm food. We keep a couple of mixing bowls next to the trash can, and dump food waste in there. We toss the bowl contents once or twice a day to make sure the system stays aerobic and isn’t stinky. Then, when the bowl gets too full for tossing, we dump the contents into the worm bin. This happens about once or twice a week.

Passing the food waste through this extra step also helps us even out the worm bin feeding schedule. It helps us average the times when we generate a bit more versus a bit less food waste.

What should I feed the worm bin?

Technically, anything organic could do. But meat and oil are troublemakers, so unless you really know what you’re doing, stay away from them. On the opposite end is manure: apparently, that is the best environment for redworms.

We feed the bin primarily vegetable waste, crushed eggshells, and coffee grounds (including filters). Because we always cook with oil, I almost never include cooked food in the compost. What you feed your bin will, of course, depend on the composition of your kitchen waste.

We always try to chop up our vegetable waste before putting it into the compost; the smaller the pieces are, the more surface area those decomposers have to work, and the faster the food waste is going to turn into great compost. We decide on how much to chop up our vegetable waste the same way we decide on how small to rip the bedding: whatever we feel like. If you spend a little less time on chopping up the waste today, it’s no big deal: you’ll just spend a little (or a lot) more time waiting for finished compost. Some people do more to help the food break down, such as chopping it fine with a food processor or blender, microwaving it or freezing it.

For the same reason, we crush eggshells before we put them in. Eggshells are apparently really good for worm bins because they provide grit, buffer pH, and slowly release calcium (a mineral which may be important for worm reproduction). Some people pulverize eggshells so that they’re practically like a dust.

Coffee grounds are also, apparently, pH buffers. At first I was hesitant to add too much because I thought coffee grounds would be acidic (because coffee itself seems to be anything but pH neutral!), but it turns out that depending on the coffee making process, most of the acid goes into the coffee itself, and the grounds end up being pretty much neutral. However, I’ve heard different things from different sources. So, I think the best thing to do is to actually measure the pH myself, but I’m not sure how best to do that. (I’ve had unimpressive experiences with a moisture meter, could a pH meter be any better? I’d love to use the little strips of pH paper we used to use back in middle school.)

All this talk of pH underscores how important it is not to let your bin get too acidic, which will kill your worms. This means being careful with adding citrus fruits, for example (we never do, but we do put in tomato bits).

Another thing with which to be careful is strong-smelling waste like onion or garlic. When we put our garlic scape leavings in the compost, it smelled strongly of garlic for weeks. I didn’t find it noxious, but I wasn’t exactly happy either.

How much/often should I feed the worm bin?

Overfeeding also results in acidity. But how much is too much? That’s something I’m still working on figuring out. You can feed half the weight of the worms per day but I have no idea what the worm population is now, and how much is too much food. Basically I feed them and check on the progress after a few days — if I don’t see any red flags then I add again. One time I saw a spot of white mold, but then it went away in a couple of days, so I figured I was safe again. Furthermore, white mold is apparently normal in a worm bin.

The biggest red flag is worms trying to escape en masse. Another red flag is an unusually large populations of anything — mold, fruit flies, mites, etc. A lot of these things are totally normal, but if there’s an absolutely huge population that you can really see, well, that could be a problem.

How do I feed the worm bin?

The conventional wisdom is to bury the food waste in your bin, rotating around several different spots. We don’t have that much room with our setup, so I have just three places where I move aside some bedding and dump the waste in. Afterwards, I cover with the bedding I moved aside and supplement with new bedding. I water down the new bedding the same as I did when I first set up the worm bin.

I use a hand fork when I work with the bin, because the idea of touching decomposing foodstuffs and squiggly worms completely grosses me out. But hey, even with my invertebrate phobia I can maintain a worm bin, so anybody can, right?

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One Response to Feeding worms

  1. stephan says:

    Thank you for that great article!

    Below you will find a list of organic products that have been sorted into a worm food rating list, to help people that are just starting out to get a good start into their worm farming project.

    The ix there as a reference for you in case you are new to worm composting or are not 100% sure if you should feed something to your compost worms or not!

    The list is a work in progress so if you can’t find the organic product that you are looking for in our worm food check list, let us know and we will add it gladly!

    In general worms can cope with nearly all garden- and kitchen waste you might offer them. Some products the compost worms can eat in large quantities and even live in them while others should only be fed in moderation.

    Especially acidic foods should be fed with care. If the acidity of your worm bins bedding becomes very high it might force your worms to migrate out of the bin to avoid death.

    Good Worm Foods are:
    Apples , avocados, bananas, cherries, rhubarb, pineapple (not the skin), peaches, pears, melons,
    Carrots, lettuce, pumpkins, sweet potatoes, beet roots, peppers, green beans, cauliflower, radishes, water cress, sugar, guavas, corrugated cardboard

    Moderately good Worm foods that you should feed in moderate quantities only are:
    Garlic, onions, lemons, olives, plums, blueberries, oranges, bread, oats, meats, fish, cake, grains, white flower, black beans, kidney beans, butter beans, nuts, wheat, bran, rice, pasta,lentils, milk, cheese, tea and tea bags, coffee and coffee filters, dog poop, grass clippings. brown packaging paper, dog poop, cat poop

    Harmful Worm food – “Foods you should not feed to your compost worms at all!”

    • Oil or oily foods (can suffocate the worms),
    • alcohol,
    • hot spices,
    • salt,
    • chicken manure,
    • vinegar

    kind regards and happy worming

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