I have done a lot of experiments feeding worms all kinds of things you are not supposed to feed them. If something is on a do not feed list, I have probably fed it to my worms successfully. But there are a small handful of things I have found that my worms would not eat. Here is my do not feed list. As I discover more things the worms will not eat, I will add them to the list.
Sugar
I have had some people challenge me on this, but my own experience shows me that worms will not eat sugar. I have been told that sugar feeds microbes, which makes a more microbe rich environment for the worms. I have found that not to be true.
Sugar may feed microbes, but it is also a desiccant and is used as a preservative, just like salt, and I believe it has the same effect as salt in the worm bin.
Osmosis is a scientific principle that says that if you have 2 solutions on either side of a membrane, say a worm’s skin, fluid wants to flow through the membrane from the side with the lower concentration to the side with the higher concentration. What does that mean in simple terms? It means that if you have a lot of sugar dissolved in the moisture in your bin, it will draw water out of the worms and the microbes, dehydrating and killing them.
Corn Syrup
After finding out that worms will not eat sugar, I was curious about corn syrup, so I did an experiment feeding worms cardboard soaked in corn syrup. The worms would not touch it. I suspect it has the same effect as sugar. This means that candy, and other highly sweetened foods, should be kept out of the bin.
Cheese
One spring, as I was preparing an outdoor bin for warmer weather, I pulled out an experiment that I had left in the bin the previous fall. It had become a slightly yellow mass full of holes. It took me a while to remember what I had put in the bin the previous fall. I finally figured out that it was macaroni and cheese. The worms had eaten all of the macaroni, and left the cheese behind. I set up an experiment with a mixture of cardboard and cheddar cheese. The worms would not touch it.
Butter
With all of the success I have had with both dairy and grease, it made sense to see if worms would eat butter. So I melted some butter and soaked shredded cardboard in the butter. The worms would not eat it.
Vegetable Shortening
I have had success feeding worms various fats and fatty foods. I was surprised to find out how quickly they devoured shredded cardboard soaked in hamburger grease. They also ate shredded cardboard soaked in vegetable oil. So I was also surprised when I ran an experiment with shredded cardboard soaked in vegetable shortening, and the worms would not eat it.
Gelatin
I was surprised to find out that worms will not eat gelatin. Gelatin is nothing more than animal protein, so I expected the worms to dive right in. They didn’t. My original experiment was with flavored gelatin. I left it in the bin for more than a month. It got very moldy, and it STUNK! The worms would not eat it. I thought at first that it might be due to the high sugar content, so I tried again with unflavored gelatin. I left it in the bin for 5 weeks, and the worms would not eat it.
If you have had a different experience with any of these foods than I have, I would love to hear from you. Let me know in the comments how you fed these foods to your worms. Perhaps I am just not setting up my experiments correctly. I will also add to this list as I find more foods that worms won’t eat.