This question comes from James, who is curious about the ideal depth for a worm bin.
The question I have for you is in regards to how deep a compost bin
should be. I’m using a basic rubbermaid bin setup that is about
10-12″ deep, and have shredded newspaper up to about 8″. Is this too
much bedding? The worms seem to only congregate on the bottom few
inches with little activity in the top layers. From material I’ve
read, the worms will typically avoid the top inch or two, but I was
surprised that there didn’t seem to be any in the middle portion of
The only guess I have is that it has something to do with the
basement temperature. I’m using a double stack method and the area
where the worms are would have an extra layer of insulation from the
cold basement air, but I don’t know how much that would affect
things. I would be grateful for any insights you might have.
A depth of 10-12 inches sounds good, assuming the bin has a decent surface area. Just to give you an example, the “new home” for my European Nightcrawlers has a depth of 8.5″, with upper dimensions of 20″ x 13.5″. I was actually very surprised to find such a perfect bin (it is a Rubbermaid Roughneck), since most Rubbermaid bins tend to be too deep for my liking.
Layering your bedding to a depth of 8″ definitely sounds good to me. When I start up a new bin I will put in enough bedding (and food materials) to bring the level close to the top of the bin. I assume you have food (scraps etc) spread around in your bin as well? Worms tend to congregate in the vicinity of the best food source and/or areas of adequate moisture. If your worms are all down at the bottom I would predict that there is something appealing down there foodwise, or perhaps that the rest of the bin is a bit too dry for them.
I personally haven’t found that worms avoid the top 1-2 inches, unless of course there is dry bedding and no food up there – again, it really all depends on the way you maintain your bin. If you bury all your food down deep the worms will likely stay down fairly deep as well, but if you layer it near the top (generally what I prefer doing) you’ll find more up there.
Unless your basement is really cold I wouldn’t suspect that their location was temperature-dependent. The warmest zones in the bin would generally be in the areas with the most microbial activity – i.e. where the food materials are concentrated.
Anyway – hope this helps, James!
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