Compost worms benefit from a balanced diet. They will eat most normal kitchen fruit and vegetable scraps. Avoid feeding the worms large quantities of meat, citrus, onions and dairy foods. Some processed food also contains preservatives, which discourage the worms from eating it. These foods won’t harm your worms, but they will avoid them and those scraps will break down and rot in the bin. The worms will eat their preferred food first but like to have some variety. The smaller and softer the scraps, the easier it is for the worms to digest and process them into castings.
Compost worms will also eat garden or yard waste, and animal manure. If adding lawn clippings take care to only add a little at a time. Fresh lawn clippings can heat up and cause problems. If you do place animal manure in your bin ensure that the animals have not been treated with anti-worm medication, as it may still be effective in their dung!
It is also not advised to use dog or cat droppings if you intend to use the castings in your food garden, as the animals may have gut parasites, which can potentially infect humans.
How much to feed worms
- Add up to 2.5cm per day
- Uneaten food should not be more than 5cm deep
- Only add more food as it is eaten
It is very important that the hungry bin is not overfed. A fully functioning bin will have up to 3kgs (6.5lbs) of compost worms. They prefer to eat their food as it begins to decompose, but not if it has become slimy and smelly. If the bin is overfed, the food scraps will begin to rot before the worms can eat them. Rotting food scraps not only smell, but also interfere with the lifecycle of the worms and the operation of the bin.
Rotting food is anaerobic – or oxygen deprived. Because worms breathe through their skin, anaerobic conditions prevent the worms from breathing properly, and may cause them to die.
Worms can eat roughly their own body weight in food a day, so make sure that you only add about the same volume of food each day as there are worms. Start by feeding the worms a small amount of food each day. Each time you feed the bin, check that uneaten food is not accumulating. You could chop up large food scraps into small pieces – the smaller and softer the scraps, the easier it is for the worms to digest and process them into castings.
Slowly increase the amount you feed the worms as the population multiplies. The worms will breed and increase in numbers to match the food supply. Building up a full population of worms (about 3kgs) can take up to six months.