WORM BIN GUIDE
Dont make this harder than it has to be.
Use this guide to build a small, manageable, indoor worm bin.
Why small bins work better
Large bins compact, go anaerobic, overheat, and are hard to maintain & harvest. Depth limits oxygen diffusion; deeper systems raise failure risk. Smaller bins are easier to correct if something goes wrong.
Worms need oxygen and consistency; shallow bins make both easier to control.
Recommended bin sizes
As long as its a solid color so light cant pass through, anything from a shoebox-size bin up to a 5-gallon bucket (filled half way) is ideal. This will keep it shallow, easy to lift, and simple to correct if something is off. Wide, low containers allow better airflow through the bedding. Very deep or tall bins are harder to manage and more likely to develop problems.
A container you can comfortably lift, tilt, and clean will get maintained, but an oversized one usually won’t.
Lids & airflow
Worms require lots of oxygen; their bedding is an aerobic system. Restricted airflow increases anaerobic microbes, odors, and stress. A solid lid can trap moisture and limit gas exchange.
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Best options:
• Screen or mesh tops (think - aquarium lid)
• Heavily perforated lids
• Light-proof covers directly on bedding (damp newspaper, burlap)
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You can build a simple wood frame with a screen fit to cover or, if using a plastic lid, remove most of the center and replace it with screen. This can be done with hot glue, or rivets.
A lid’s purpose is keeping pests out, not keeping worms in. Healthy conditions keep worms in the bin.
Drainage
Bottom holes are not required. Vermicompost should be at “wrung-out sponge” moisture. Excess leachate indicates overwatering and increases anaerobic conditions.
If liquid is pooling, conditions are already off balance.
Bedding + fill depth
Keep material loose and fluffy. Do not exceed ~8 inches of active material to maintain airflow and microbial balance.
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Click here to learn more about bedding - approved materials, how to prepare, etc.
Air spaces are as important as food.
Finished castings
When the original bedding is mostly gone and everything looks uniform and soil-like, it’s time to harvest and reset. Worms need fresh bedding and food to stay healthy, and finished castings should be removed and used rather than left to compact.
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These are the three least-invasive options:
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Migrating
Add a second bin with holes and fresh bedding/food on top. Worms move up over time out of the castings. This method is slow and can be incomplete, with many worms straggling behind. -
Baiting
Pause feeding, then add a concentrated food source to one side. Most worms will congregate there & you can scoop them out. Also, not a complete method. -
Separating
Dump contents into small piles under bright light. Worms move downward; remove castings gradually until only worms remain. This has a near 100% success rate, but requires the most work.
There’s no perfect harvest method. Choose based on time, patience, and how many worms you want to save.