Did you know that worms love coffee grounds? That’s why adding coffee grounds to your worm bin is a great way to increase the amount of organic matter in your compost. But, how much coffee ground can you feed worms?
You can feed worms a half pound (0.23 kg) of coffee grounds a week, but their diet should consist of no more than 50% coffee grounds. Worms need about one pound of food a week, but there should be various types of food, including fruit and vegetable scraps and eggshells.
You may find that the worms in your compost bin or garden don’t care much for the taste of coffee grounds, and that’s normal. Below, I’ll talk about the different foods you can feed your worms, how much of what to give them, and what to look out for in overfed or underfed worms.
How Much Coffee Grounds Your Worms Can Eat
As humans, we can only consume so much coffee.
Many studies have cited the benefits of drinking coffee, but there’s no reason for us to make it a staple of our diets or create an entire food group for it (though I know some coffee addicts who may argue that point).
Worms can consume about half their body weight in organic matter each day. So, if you have a bin that weighs eight pounds, your worms could theoretically consume up to four pounds of food waste every 24 hours. This includes:
- Coffee grounds.
- Fruit and vegetable scraps.
However, you shouldn’t feed your worms more than 50% of their diet on coffee grounds. The scenario above with the eight-pound (3.63 kg) worm bin would mean no more than two pounds (0.9 kg) of coffee ground.
It’s better, though, to err on the side of caution and give your worms even fewer coffee grounds than 50%. Try to start at about 25% and work your way up. You might find that your worms don’t like coffee grounds that much, and 25% is too much filler for them. You can keep testing it out on newer worms as they’re born to see if the younger generations have different tastes.
The Reason Worms Can’t Have Too Much Coffee Grounds
You may know a friend or family member who is caffeine sensitive and therefore can’t have coffee, or who has stomach issues from a cup and decides to opt out of any coffee rituals (you, yourself, may be this friend!)
With worms, it’s not as complicated. It won’t give them caffeine anxiety or the jitters, and it doesn’t make them need to run to the bathroom. Coffee grounds have their fair share of nutrients, and your worms will enjoy breaking it down.
However, a balanced diet will help them work at their best. There is too much of a good thing, and coffee grounds might be one of them for your worms.
The Downsides to Composting Coffee Grounds
If added in excess, coffee grounds can also make your soil pH too acidic. No more than 30% of your total compost volume should be coffee grounds. Yes, composting can be a lot of math, but it’s worth it!
Think of it this way: if your compost is 50% worms, and you’re only giving them 50% of their body weight in coffee grounds, you’re only at 25% of your total compost coffee grounds.
Soil pH is a huge determinant of how many nutrients your plants are getting. A soil pH that’s too high or too low makes it nearly impossible for your plants to absorb the nutrients they need, even if there are high concentrations in the soil.
If you’re vermicomposting, you’re likely very interested in your soil becoming nutrient-rich so that your plants can grow faster, stronger, and healthier. Unfortunately, if you add too many coffee grounds in hopes it’ll make your worms hyper and happier to break down nutrients, it won’t work. Additionally, an extra-acidic soil pH can even injure your worms!
A little bit is okay and will keep your worms happy, but too much will affect the soil pH.
How To Feed Your Worms Coffee Grounds
Coffee grounds can be served to your worms, whether wet or dried out. I’ll add a caveat to this: adding a sopping wet pile of coffee grounds to your soil might cause waterlogging.
If you mix it with a spade or even a stick, you risk puncturing your worms and hurting them. If you choose to use wet coffee grounds, spread them out evenly while still leaving room for air. The rest is easy if you’re ready to get the ratio right for your worms.
Another option is to dry your coffee grounds out. This is also easy; just set your coffee grounds on a pan, some newspaper, or a paper towel. You can place it in the sun, and it’ll dry up in no time.
What Types of Coffee Grounds To Feed Your Worms
Another great piece of news: worms don’t care much what coffee grounds you feed them. If you consider yourself a coffee snob and only drink imported coffee, freshly ground down from beans, it won’t make much difference to your worms.
They’re okay with your generic, instant, burnt, all of the above! No studies have yet found any results about whether or not more expensive coffee beans are better for your worms. Don’t let this stop you from experimenting yourself, though!
What Should I Feed My Worms?
If you thought you could just take your morning coffee grounds out to your worms each day and they’d be set, you’re wrong! There are many other things worms need in their diet. So, what else should you feed your worms?
You should feed your worms a balanced diet of food scraps, including coffee grounds, fruits, vegetables, and other compostable foods. You can also buy supplements to richen the nutrients in their diet.
Additional things you can feed your worms include:
- Coffee paper filters
- Tea bags
- Tea leaves
- Shredded newspaper
- Paper egg cartons
Avoid things like meat, dairy products, oils, or plastics, and always err on the side of caution if you aren’t sure whether or not something should be composted.
The important thing is to ensure that you’re giving them a variety of food so that they stay healthy and happy. This will also help to reduce your food waste.
If you’d like to learn more about food scraps not to feed to compost worms, you could check this article out: 11 Food Scraps Not to Feed Compost Worms
How Much You Need To Feed Your Worms
As I’ve already mentioned, the general rule is to feed your worms about one pound of food per week. This includes both fresh and decomposed organic matter.
So, if you are adding a bunch of fresh coffee grounds to their bin, you will want to cut back on other foods that week. The same goes for adding a lot of decomposing matter like fruits and vegetables.
You don’t want to overfeed them, or they will start to produce too much compost. Too much compost can harm your plants because it contains too many nutrients.
If you are unsure how much to feed your worms, it’s always better to err on the side of caution and give them a little less than too much. You can always add more if they seem to be doing well.
One way to tell if you’re feeding them too much is if their bin starts to smell bad. This means that there’s too much decomposing matter and not enough airflow. If this happens, you’ll want to remove some of the compost and add more fresh organic matter, like coffee grounds or leaves.
How To Know if You’re Overfeeding or Underfeeding Your Worms
Determining whether or not you’re overfeeding or underfeeding your worms isn’t too difficult. Worms know how much they can eat; unlike humans, they don’t often overindulge. They eat as much as they can and leave whatever else to rot. If you’re overfeeding, you may notice:
- Foul odor (it’s not coming from the worms, it’s coming from the rotten food they aren’t eating).
- Leftovers in your bin.
- Molding food.
You can also tell if you’re underfeeding if you’ve noticed the food you give your worms is gone or consumed halfway through the week. Additionally, your populations won’t likely thrive.
Worms are nature’s recyclers, so by feeding them coffee grounds, you’re helping to reduce waste and create nutrient-rich compost for your plants!
However, don’t overdo it. Start with 25% of their food being coffee grounds (or less) and work your way up from there if they love it.
Don’t give them more than 50% coffee grounds, or they won’t be able to fit helpful nutrients into their diet. Additionally, you want diversity in the nutrients they break down, so make sure to give them that!
You can read my other article on how much to feed to composting worms here: How Much to Feed to Composting Worms (Beginner’s Guide)