Adding a Tray to your Worm Bin

It's been 6 months since we set up our indoor worm bin, and it's become part of our home. We are so used to having it set up in the living room, in a dark corner, that we tend to forget it can be considered an eccentric novelty by visitors. We still get subtly confused looks when someone comes over and asks about that little box on legs--"It's our worm farm!" I'm not sure if those are looks of surprise we are seeing on the faces of friends, family members, and neighbors, or if it's slight horror. "Worms? In your house?" I love those shocked-and-somewhat-horrified reactions because there is nothing at all like a curious mind to provide a teachable moment. "Yes, they are amazing, and the easiest pets we've ever had. They make no noise, no smell, they eat our garbage, and we can ignore them for days at at time. The best part? They give us perfect food for the garden!"

I'm hoping that anyone who has a garden (or even houseplants that they take pride in) will see how easy a worm bin can be and how wonderful it is to have a steady supply of castings available. It would be so awesome if I could convince lots of other people to keep worm farms in their own homes.

Our worm bin is tucked nicely in a dark corner,
barely noticeable but always working hard.
Can you even see it?

Obviously, we love our worms. We saved up for our bin for quite some time; here is the one we purchased. I cannot emphasize enough that homemade bins are perfectly acceptable, and we plan to make one ourselves similar to the plans here, or here, or here. Those links show how to use a tote; check out how my friends at Future Farming used an old utility sink for their worms, here! There are also easy ways to set up worm bins outside, like this one.

The biggest benefit to a commercial bin like ours is that they usually come with stackable trays, which allows for more composting to occur at once, and makes it easier to harvest the worm castings (no digging through worms and sifting leftover scraps to get your castings).


If you have a commercial worm bin, you probably got a lot of information along with it. A booklet, a pamphlet, or maybe even a video. The simple act of giving worms rotting food suddenly looks like a science experiment when you start going through the information. I was feeling a bit a bit confused and flustered when it came time to add a new tray, and the video I got wasn't as detailed as I'd like, so I outlined the task in 5 simple steps.


1. Stop feeding the worms. Withhold food and remove any huge chunks that are in the bin for your regular compost. As long as you have ample carbon (the easiest for us is shredded paper), the worms will not starve, because they can always turn to the carbon for food. I stopped feeding a week before I planned to add a new tray; there was still a little food in the bottom tray.

Under a thick layer of shredded paper in our original tray, the worms have been eating scraps
and making castings for months. I stopped adding food to get ready for a new tray.

2. Find bedding for the new tray-think carbon. When a couple weeks went by without adding food to the bin, we added our new tray. When I added the new tray, I was able to pull off the top layer of carbon from the old tray in hunks and put the paper right on top of the new bedding. Though you could technically use shredded paper exclusively as your bedding, it's good to add coconut coir or soil, too. I avoid adding soil only because my bin is inside and I am afraid of bringing in too many unwanted critters. I got a supply of coconut coir with the bin and plan to order these when I need more. A little coconut coir goes a long, long way! Just a tiny bit of it expands a lot when water is added.


*NOTE: In the below photo, you can see I added carbon and bedding to the tray with NO layer of newspaper under it. This is what the video and instructions that came with the worm bin instructed. However, I do recommend a layer of NEWSPAPER under any new tray you add. Each tray will eventually end up at the bottom of the stack, and with no barrier, the worms will try to escape. Trust me, I know this! Adding just a sheet of newspaper to the bottom of each new tray will not prevent the worms from moving up and down through the trays; worms are very determined creatures.

Filling up a new tray with coir and with shredded paper. I filled it until
the bedding went halfway up the sides of the tray. Put the tray over newspaper as you work
to keep the bedding from sprinkling through onto the floor.

3. Put the newly filled tray on top of the old tray.

4. Add a nice buffet of food to the new layer. Don't forget; no citrus, meat, dairy, onions, or hot peppers! Also, a good sprinkling of eggshell powder will keep those worms happy; it promotes a perfect pH level to prevent outbreaks of mites or springtails, and the worms LOVE eating it. Cover the food with carbon and incorporate the carbon into the tray by gently raking it in a little. If you make sure to cover all the exposed food with bedding, you'll have less risk of unwanted pests.

Coffee grounds with filter included, tea bags, tomato, potato, cucumber,
and chopped up banana peels...it's a worm FEAST!

4. Place slightly damp newspaper over the new layer. Not too wet! We give the newspaper a little spray of water and tuck the worms in. This helps keep a moist, dark, happy place for the worms.

5. Give the worms a week or two to vacate the old layer, then harvest the castings in that layer. We left the bottom layer for a couple weeks, checking on it occasionally. At first the worms hung around in both layers, finishing off the food in the old tray and migrating up to new offerings. In time, the worms exhausted all food options in the bottom layer and were mostly in the top layer. That happened right as we were planting our fall garlic, so we took the bottom tray outside to the garden and top dressed the newly planted garlic bed with the castings.

*You can store your worm castings in a container that has ventilation. We used an old cat litter box with some holes drilled into the lid. If you store the castings in an airtight container, you can create a stink; microbes are still at work breaking down the small amount of partially decomposed plant material in the castings. In an airtight container, anaerobic organisms can take over and the whole thing can become a stinky rotting mess. Keep the aerobic microbes happy with some air! You also don't necessarily want the castings to dry out completely, so it's also a good idea to place a damp layer of newspaper over the stored castings before putting the vented lid on.

We store the harvested worm castings that we aren't using yet
in a re-purposed cat litter box, with holes drilled in the lid.

5. Add new trays when needed or wanted. If you know you want to harvest castings soon, work around your own timeframe. You can stack up all your trays and have them all working at once for a bigger amount of castings all at once--each layer will have various stages of compost going, with the bottom always being ready to harvest first. We are still working with two trays at a time, but the bin came with a total of 4, so in time we hope to have it towered up and working to full potential. With winter coming, we want to get the worms working hard to provide plenty of garden nutrition that we can use when spring comes and next year's garden is ready to be fed!

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