Do Worms Eat Microbes or Wastes or Both?

Really great questions from Sherman:

Hi, I read that red wigglers consume microorganisms rather than food waste so how does having more worms consume food wastes faster?

What types of kitchen food waste’s good for supporting the microbial population?

Hi Sherman,

Thanks for writing in – this is a really interesting topic for discussion for a number of reasons.

OK – let’s start with microbes as worm food…

Yes, it has been shown that worms derive much of their nutrition from microorganisms that have colonized decomposing organic matter. I think part of the problem here is that these worm composting facts – in this case legitimately based on actual scientific research – can be viewed in too-rigid a manner. i.e. Worms eat microbes, that’s all they eat, and THAT’S THAT!!

While I would absolutely agree they likely get most of their nutrition from all those microbes – the fact is, they are definitely consuming more than just microbes (thereby getting nutrition from more than just microbes as well).

The microbes are using enzymes to break down the food materials – in the case of fruit and vegetable wastes, for example, this would involve the rupturing of cell walls, and the release of water (along with plenty of nutrients for the microbes to “feed” on). So you kinda end up with this slurry of stuff (for lack of a more scientific term – lol) that’s full of microbes.

Well, picture the worms coming along like a Hoover and sucking up this slurry, microbes and all. Yes, much of the nutrition will be locked in the microbes themselves, but there’s no doubt they are ingesting a lot of the waste material as well.

It’s as though the microbes are softening the food for the worms, and the worms are saying “thanks” by eating them. lol

OK – on to worm numbers and how that affects processing speeds…

In theory, if there are more worms there are more “mouths to feed”, so more wastes can be processed. In a well established system, using foods that have been well-optimized (i.e. made even more microbe-and-thus-worm-friendly), this can definitely be the case. But the problem is that people (often newbies) tend to take this too literally – assuming they can start a system with loads of (usually poorly optimized) food wastes and loads of composting worms, and that everything will work out great as a result.

Unfortunately, that’s very rarely how it will actually work. What usually happens in cases like that is that the food wastes become foul, heat up, give off toxic gases etc, causing the already-stressed worms to either die or attempt to escape the system.

My recommendation is always to start with a modest population of worms, and modest amounts of optimized food materials (along with plenty of bedding), and to gradually ramp things up from there. These worms will grow and reproduce very quickly when they are provided with a scenario like this – and you can end up with a large, thriving population of worms that CAN process lots of wastes quite quickly.

Let’s talk briefly about kitchen scraps…

Obviously, the usual composting rules aside (i.e. “no meats, dairy etc”), ideal kitchen scraps are those that come from water-rich foods (fruits and veggies), and that have been optimized for microbial colonization. Something like a whole carrot, for example, is pretty much useless as a worm food. For one thing, it’s a root vegetable so it is designed for life in soil! If anything, it would probably start growing in your worm bin. lol

When you chop, freeze/thaw, cook, age etc resistant wastes like this they become exponentially more microbe-and-worm-friendly (especially if you use a combination of tactics). As alluded to, some scraps need less optimization than others. eg there is a big difference between putting some rotting lettuce, or a slice of watermelon into a worm bin, and dropping in a whole potato!

And speaking of potatoes…

Starchy wastes – especially ones high in salt – are a lot less ideal, but it is still possible to process them (in moderation) in a vermicomposting system. The best approach is to chop them up really well and mix them with the variety of other optimized wastes.

Anyway – I hope this helps, Sherman!

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  1. Thanks but one thing that concerns me is what causes food wastes to become foul and release poison gases?

    • Steve
    • October 26, 2015

    Optimizing food waste (since that is often a primary food source for aspiring worm farmers) cannot be stressed enough. I initially struggled a bit by not using enough carbons to buffer the food. My first attempt was ALL food waste. Overheating and rancid odors from anaerobic activity marked that learning experience, along with killing off my first batch of worms. An abundance of all-important carbons (like shredded cardboard) will make an oxygen-rich environment, more favorable for the aerobic microbes and the worms.

    • Bentley
    • October 26, 2015

    Hi Sherman,
    Likely the most worrisome gas is ammonia, and it is released when there is excess nitrogen (i.e. when the C:N gets too low) AND when pH gets too high.
    The key is to make sure you are including plenty of bedding materials (as Steve mentions in his comment), and are providing plenty of air flow. You more than likely won’t need to worry about the pH getting too high (often on the acidic side), but be a bit careful with alkaline materials like calcium carbonate.

    • Judy Rhodes
    • September 6, 2016

    How often should I add additional bedding, such as peat moss, dried grass, leaves. Should they be mixed together and added or added separetly?
    Thanks for the help.

    • Steve Bichlmeier
    • September 6, 2016

    Judy, you should add carbons with every feeding. You can layer them just below the food waste you are adding OR mix carbons with the food waste. Personally I prefer mixing food waste and bedding together, plus having a generous layer of bedding on the surface. The dried grass and leaves will soak up excess moisture. My favorite buffer, shredded cardboard,will provide a time-release food too and more airflow than leaves, since they have a tendency to mat together. I’m hesitant about using peat moss because I understand it contributes to the environment’s acidity. We want a more neutral pH for optimum worm activity.

    • Lowell
    • May 19, 2020

    I soak my cardboard and shredded paper in hot water and rinse several times then i soak the bedding with blended up food scraps like mellon or old juice. The worms eat the bedding and it creates no spoiled odors or gas. Carbon mix with the food.

    • Myrna
    • September 21, 2020

    You talk about peat moss not being of your preference due to acidity, how about coco coir from a good source?
    Also, I am terrified of filtering the castings. I only started with my worm farm st the beginning of May, is it necessary to collect the castings at a certain time?

    • Bentley
    • October 10, 2020

    Hi Myrna
    I am even less of a fan of coco coir. It tends to be pretty expensive, but in comparison to something like shredded cardboard, the worms don’t even seem to like it all that much. I might use it as a filler bedding for water retention, but I really love my paper-based beddings. Make sure coir is really rinsed well since it can contain salts which are harmful for the worms. Not sure what you mean about being “terrified of filtering the castings”. There is no set timeline for harvesting, but you may see a decline in habitat quality if you leave the bin going for too long without any sort of overhaul (or harvest).

    • CTwormwoman
    • February 2, 2021

    I realized the post originally started by Sherman is now 6 years old. But, it is as valid today as it was 6 years ago. I absolutely concur with what Bentley said. while worms definitely eat the microbes, they also eat the actual food source. The best proof of this is how the color of the finished castings represents the color of the food fed. For example, I have red wigglers under my rabbit cages. They are eating exclusively worm poop.
    Now that truly is BLACK gold.
    The three worm bins I have inside my home are living in a coconut coir, shredded corrugated cardboard and shredded newspaper base, and their added food is whatever scraps I have. However, when I want to finish off a bin because I want to harvest it, I stop feeding for a few weeks and the worms will eat whatever paper or cardboard is left. The castings they produce when I add food are much darker than the castings they produce when they are eating just cardboard and paper. Those castings are brown, not black. Clearly that is not a result of the color of the microbes but Rather the color of what they are eating. No different than humans. What we eat is often represented in our waste.
    As for the strong odor, I believe Sherman is referring to fermentation. The natural process that happens to all fruits. To me, if fruit is fermenting in a bin There’s a couple of possible causes.
    1)too much was added at once, and it began to ferment before the worms could consume it all
    2) The fruit was not in the condition for the worms to start eating it. Meaning, a whole apple without any decay was put in the bin rather than a chopped up apple that had been in the freezer and then thawed.
    3) If you feed nothing but fruit consistently, it can cause the conditions of the bin to become acidic. The result of that is worms that will eat less and reproduce less. The bigger problem is acidic beds tend to be aerobic in nature and things go downhill fast. Potworms explode in numbers and worm mites will show up when they were never a problem before.

    This is my experience anyway.
    38 years of it – dang I’m getting old lol

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