Worm Café wormery with 2 trays and a tap

The tub takes up roughly 56 cm by 38 cm of floor space and stands 66 cm tall, so it covers less than half a square metre. You can set it up in a kitchen, a utility room, a cellar or a garage, and outdoors as long as it is protected from strong heat. Choose a mild spot, out of direct light and away from the vibrations of a washing machine or fridge, which the worms avoid. If you place it in a garage, raise it slightly to keep it away from exhaust fumes. Its feet hold it clear of the floor, which limits access for ants, and at 7.1 kg empty, it is easy to move as long as the trays are not loaded.

At the start, you place just one tray on the juice tank. Fill it with a bedding layer of about 5 cm of non-corrugated brown cardboard, egg boxes or paper torn into pieces, moistened until it has the texture of a damp, wrung-out sponge, along with a handful of compost or potting soil. Place the worms on the surface and let them burrow down by themselves, then wait a few days before the first feedings, which should be small and finely chopped. Increase the quantities as the colony multiplies, and allow 3 to 4 months for a wormery to reach its optimal performance.

Your bin stays balanced if it receives roughly one third dry material to two thirds wet material. Fruit and vegetable peelings, raw or cooked, leftover rice or pasta without fat, and coffee grounds provide the moisture; plain brown cardboard (not corrugated), egg boxes, undyed kitchen roll and paper coffee filters provide the dry material, while corrugated cardboard stays out, since its glue would end up in the compost. Cut melon and squash rinds and cores into pieces of 2 cm at most. Keep garlic, onion, leek and shallot out of the bin, as they act as wormers, along with citrus fruit, meat, fish, dairy products and fats. An unpleasant smell almost always points to waste that the worms cannot keep up with or to bedding that is too wet: reduce the feed and add dry material.

After 3 to 4 months, the material in the bottom tray looks like fine compost and contains almost no worms: the vermicompost is ready. To encourage the last occupants to leave, place this tray at the top of the stack with the lid left open, and the light will drive them down into the trays below. Then mix the vermicompost with roughly two-thirds soil or potting compost for your plants and planters, and ideally use it within 6 months. The tray you have just emptied goes back on top, ready to receive the next additions. While you are away, the colony can go 3 to 4 weeks without being fed.

The liquid drawn off at the tap is reserved for watering the plants and is not poured into the fish water, whereas compost tea is made from fully mature worm compost: a few large handfuls enclosed in a mesh bag steep in 20 litres of water, continuously stirred by an aquarium air pump, for 2 to 3 days, then the liquid is strained and diluted at 1 part to 10. It is applied as a drench at the base of the plants, and if it does reach an aquaponic system, it is only in small doses, around 50 ml, watching how the crops respond before adding more. Continuous aeration prevents oxygen-free fermentation. The worm composting guide details its other uses, and the article on deficiencies in aquaponics helps you recognise them on the foliage.

The box contains the lid, the 2 working trays, the liquid collection tray, its tap and the 4 feet, along with a worm composting guide and assembly instructions in French. You assemble the unit by hand: the tap fits onto the liquid collection tray, the feet go under it, then the first tray and the lid are put in place. The worm composter is designed by Tumbleweed, made in Australia from 100% recycled plastic, and comes with a 2-year guarantee. For the dry material in the first few months, a bag of coarse sawdust is a useful complement to non-corrugated brown cardboard.