Over feeding compost worms is THE most common mistake that’s made with worm composting in bins and tiered worm farms.
“Get a worm farm” they said. “Put all your kitchen scraps in it” they said. “It’ll be fun!” they said.
And it was.Until eventually the whole thing became a sodden mess.And most of the worms went away.And the fun want away with them.
Chances are very high this was because we over fed them.
Getting the feeding right is important and with a key piece of information it’s also easy. But without knowing what’s too much for your worm bin, getting it wrong is just as easy. So let’s clear this up.
Why feeding compost worms the right way is important.
Your worm compost is a living environment of worms, tiny bugs and microbes. All working together to turn the bedding and your food scraps into the best plant food, soil builder and pest & disease control on earth.
All these critters are contributing to this process. And the idea is to have an aerobic (ie need air to live) environment so that the microbes are the beneficial ones. This is another reason worm castings are so amazing.
Putting more food in a worm bin than this living eating composting environment can keep up with brings the risk of anaerobic (ie need a lack of air to live) microbes getting established, as well as the risk of the whole environment losing air flow, which adds to the anaerobic microbe risk, and then comes the follow on effect of lowering the pH of the bedding below what this composting environment is suited for.
The short way to say that is, the worm bin can “go sour.” The worms can’t live in this environment and they will leave if they can or die off if they can’t.
How much should I feed my compost worms?
A compost worm will eat about 1/4 to 1/2 of it’s body weight in a day.A compost worm on average will weigh about 1/2 a gram.
Doing a calculation here is easy if you know how many worms you put in your worm bin. 1,000 adult compost worms, in general, is around 500 grams of worm composting power. And they’ll work through 125 grams to 250 grams of food each day.
Feeding compost worms once per week rather than every day is better for the whole worm composting environment. So multiply the above by 7 and you have the weight of food scraps to feed 1,000 adult compost worms each week.
Always err on the side of caution here. There’s always the possibility that your 1,000 adult worms weigh a good deal less or more than 500 grams.
Not sure all your worms are adults? Or nervous after a previous worm composting attempt that went badly? Then go with the 1/4 calculation while you get familiar with them and just how much they will get through in a week. They are composting everything in the bin, not just the food you add so they aren’t going hungry while you work on getting this part right.
If you have no idea how many worms are in your bin, then no calculation can be done. Instead, use visuals. Get an idea of the amount of the next feed you give them. Then a week later have a good look through the bin and see how much is left over. If there is food left over, feed a little less next time. If there are only skerricks left, you’ve got the amount about right. If there is nothing to be seen, feed a little more next time. Caution is key.
Whether you are measuring the food or not, know haw many worms you have or not, the guide to follow is:
- Food left in the worm bin when you next feed them = they are not keeping up. Feed less next time.
- No food left at the next feed = they are keeping up.
In optimal conditions your worms will roughly double their population in 90 days. So each week that you feed them, they will eat a little more. Over time you’ll find you are able to add increasingly more of your scraps into the worm compost.
What can and can’t I feed to my compost worms?
Compost worms will eat anything that once was living and is now decomposing.
Actually, the compost worms are eating the microbes that are eating the decomposing matter.
That said, when your worm bin is a contained environment like a storage tub or a tiered farm or a hanging bag, AND when the compost itself is still relatively new, there are some things we should just leave out of the worm bin to prevent possible problems. Whereas if your worm bin is 12 feet long, you’ll be able to put just about anything in there. This kind of size enables the worms to move away if need be, until the microbes have begun the decomposition process and it becomes ready for the worms to move in on.
| Do feed | Don’t feed |
| Kitchen scraps | Fresh manures (except rabbit) |
| Garden trimmings | Meat-eating-animal manure |
| Waste from food harvest | Citrus and Onions |
| Aged horse and cow manure | Meat, Oils, Dairy |
| Rabbit bedding | Dead animals |
| Non glossy paper and cardboard | Freshly cut lawn clippings |
| Used coffee grounds | Anything you don’t want in your garden |
| Hair from pets or your hairbrush |
Over time the worm compost microbial environment gets richer and better at managing foods like citrus and onions. While the compost is under a couple of months old and while you’re getting familiar with the process and the worms behaviour, stick to following these lists.
The effort, which isn’t that much in the grand scheme of things, to do a great job of worm composting means you’ll have all the benefits of worm castings in your garden for as long as you keep the worm compost operating.
