Discuss what worms need to survive (ideally through close observation of a worm)
Air: the bin has holes in the lid, and the lid will be opened frequently to allow more air in too.
Water: worms need to stay moist (as they breathe through their skin, obtaining the oxygen dissolved in the water)
Food: worms eat rotting plants which are soft enough for the worm to ingest (and turn them into rich soil)
Darkness: worms burrow down away from the light to seek cool, damp places, and to hide from predators
Assemble the bin as a class
Sit the class in a circle around the empty worm bin, and assemble the bin step by step to provide the worms with what they need to survive.
1. Worms need a moist environment - make a layer of wet newspaper in the bottom of the bin to keep the environment damp: distribute trays of water around the circle. Distribute a sheet of newspaper to each student. Ask the students to lay their newspaper sheet in the water, then crumple it into a loose ball (about 5-10cm diameter) to gently squeeze the extra water out. Pass around the worm bin for students to add their wet newspaper balls to it, to make a layer of wet newspaper balls covering the bottom of the bin.
2. Add the worms: add the red wigglers/small garden worms in a little soil. (Students can also add worms they have been looking closely at.)
3. Worms need food: students can each add a piece of old vegetable to the bin, to form a scant layer. Do not add to much as mould growth on the uneaten vegetables can take over the worm bin. Avoid sweet fruits (apple cores, banana peels, orange peels) as this attracts fruit flies.
4. Cover the soil to keep it moist: students tear newspaper into long strips, then layer this on top of the worms and their food. This keeps the moisture in and any fruit flies out. It also makes a dark space for worms to crawl around in and find food.
5. Place the lid on. Air will enter through small holes in the lid, or a tightly-sealing lid should be opened periodically to let fresh air in.
Discuss long term care of the worms
The bin should be kept out of direct sunlight and away from heaters, to keep it cool.
Food should be added when the worms have consumed the previous food. Too much food will invite mould growth.
The bin should be kept damp but not soggy: worms need to stay moist, but will drown in too much water. Any added water should be chlorine-free.
When the newspaper strips are getting broken up, mix them in and add a new layer on top.
After a month or so, the worms will have made new, rich soil from the vegetable scraps. This soil can be added to garden or potted plants as fertilizer.
Sometimes, plants will grow from the seeds added to the bin (see third photo).
See the worm bin care sheet for more detailed information (attached).
Also more information here: http://compost.css.cornell.edu/worms/moreworms.html
Dismantling the worm bin
When the worm bin is taken down, the freshly made compost/rich earth can be separated from the worms and put on plants that need fertilizing.
Look out for baby worms, and even worm eggs (about 1mm long, dark red-brown and egg shaped with one pointed tip) - see photo.
The worms can be put in a garden, or kept to make a new worm compost bin.
Setting up a second compost bin, from a previously made compost bin:
As above, make a layer of wet balls of newspaper in the bottom of the new bin. Take several handfuls of soil, rich with worms, from the old compost bin (you could use the entire bottom layer of soil and worms if this layer is not too deep). Layer over the old vegetables and dry newspaper etc, as described in the instructions above.