I have used worm bins before that we premade with plastic. They were nested bins such that the bottom of an upper tray was directly touching the scraps piled up in a lower tray. Worked well! Now at a new place I built a basic worm bin with wood, based on designs I found online. It looks good but I am unsure of the gap between bins. Here's photos then details on the gaps:

Bins being constructed

first gap on side of boxes

bottom gap between boxes

The first picture shows the basic idea with these boxes. There will be 3-5 boxes total, depending on decomposition and fill rates.

The second picture shows the gap I am most concerned about, gaps between the boxes. The wood and my carpentry is not perfectly straight, so the frames don't sit entirely flush with each other. Most of their sides touch but there are corners and some sides that are separated. Is this an issue for worms (migrating between bins, or being happy with their climate)? If you think it matters, any tips for covering the gap? I would think the gaps improve airflow which is good, and the worms can still travel between bins on the touching parts.

The third picture shows another gap which I think is less of an issue. Because the bins are not nested, the contents of the lower bin are only in contact with the mesh-bottom of the bin above it if the pile exceeds the height of the lower bin and gets pressed down. That is not the case now but will be over time. Is this gap something also important to avoid, or is it not an issue?

Time will tell but I wanted to get others' insights on this too as I start the bin. I will be using a combo of European nightcrawlers (earthworms) and red wigglers. Bedding is mix of soil and rotting coarse sawdust, input is uncooked organic veggie and fruit scraps sans citrus.

  • Try it and see, it will depend a lot on conditions where the boxes are placed. I'd be inclined to put newspaper over the gap on the inside to reduce air movement. If you can keep your current farm running as a backup in case it doesn't work that would help.
    – Móż
    Mar 14, 2021 at 0:57
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    @Móż I am testing it out and will report back on what I find. Crumpled newspaper in the gaps could work, we'll see how cumbersome it is to repack every time the boxes get lifted but that shouldn't be too often. Sadly my other worm bin is no longer in service - starting anew with this one.
    – cr0
    Mar 14, 2021 at 17:23
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    also, it might be possible to unscrew/lever apart the top right end joint in the middle photo so you get a small gap there rather than a big gap on the other side. It is probably not too late to just put the stack on hard ground and stand on it to force it all into the same degree of not-quite-square :)
    – Móż
    Mar 16, 2021 at 0:42

1 Answer 1


A too large gap could dry the system, but I think it is fine as it is in your picture, except if you bring too much dry waste. Just keep an eye on it from time to time to be sure that moisture is still there on the internal wall. But as you said, ventilation is important in vermicomposting.

The main issue with such a hole is that flies can come to lay their eggs and then you could have many of them. If you don't care, it is fine; if you care, then it is fine only if you bring non-sweet waste mostly.

Small rodent may also try to pass in to snack some worms...

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