DIY worm bins can be made from recycled containers such as plastic tubs or boxes, dustbins or water butts - here are just a couple of simple ideas to give you inspiration. (See our post on Worm Composting for more details of how to feed and take care of the worms.)
Single unit method
For this you will need a plastic dustbin (or a wooden or plastic box with a lid) to keep the worms in and the rain and flies out.
Drill drainage holes around the base about 5cm up and about 25cm apart. Then drill some small holes 5cm down from the top of the bin as air holes. Stand the bin above a tray to collect the liquid plant food which leaches out as the compost matures.
Or, as an alternative to drilling holes, fit a plastic drainage tap (use a water-butt or home brewing tap) close to the base of the bin to draw off the liquid plant food produced as the compost matures.
Put a 10 cm layer of gravel in the bottom, then cover with a layer of fibrous matting or a close fitting circle of wood or plastic with holes drilled through for drainage. Add a 7-10cm layer of moist bedding material, such as leaf mould, well rotted compost, or moist shredded paper, and the bin is ready for the worms.
Tiger worms or brandlings can be harvested from an existing worm bin, a manure heap, or a mature compost heap, or you can get them from fishing tackle shops, worm bin suppliers or online. (Wormcity sell composting worms and also a complete wormery starter kit containing worms, coir bedding and worm food on Amazon)
After adding the worms, put just a handful of kitchen scraps in a corner of the bin and cover everything over with moist newspaper, cardboard or shredded paper. Put on the lid and leave undisturbed for a week to allow the worms to settle in. Gradually build up the food supply as the population of worms increases.
This system uses three 8-10 gallon plastic stacking storage boxes - the sort often sold for storing toys. They should be opaque, not see-through, and should stack quite tightly inside each other. You will only need one lid. More layers can be added later if needed.
Drill about twenty evenly spaced 1/4 inch holes in the bottom of two of the boxes. These will provide drainage and allow the worms to crawl up through the compost from box to box so you can harvest the castings.
Using a 1/16 inch bit, drill ventilation holes about an inch apart near the top edge on each side of the two boxes, and drill about 30 small holes in the top of the lid.
The bottom box just needs one hole at one end for drainage.
To begin with you will just need to use the bottom box, one of the boxes with the holes, and the lid.
Sit the box with holes inside the bottom box. Place a 3-4 inch layer of bedding material in the top box. This needs to be moist but not soggy. Use moist newspaper or shredded paper fluffed up and if possible add some leaf litter or well rotted compost, plus a little garden soil to provide grit for the worms
Next add your worms to the bedding with just a small handful of kitchen scraps. Cover with some moist cardboard or shredded paper and put on the lid.
Place the worm bin out of direct sun in a well-ventilated area such as a utility room, shed, or garage. This system is not rain-proof so is not suitable to sit outside.
Leave for a week then feed the worms just a little at first, placing the food under the cardboard. As they breed, slowly increase the food supply. Collect any liquid that drains from the bottom box - 'worm tea' is a good liquid fertiliser when diluted with water.
When the first box is full add the next box by sitting it directly onto the surface of the compost in the first box. Add some food scraps and cover with moist cardboard or shredded paper to get this box started and put on the lid.
Over one to two months the worms will gradually migrate up through the holes to the fresh material leaving behind almost worm-free vermicompost in the bottom box ready to be harvested. (You can rescue any worms that might remain and put them back in the bin. Tiger worms live naturally in compost or manure heaps, not garden soil).
See also Worm composting; Worm compost troubleshooting