What to feed your worms
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.
Most fruit and vegetable scraps
Citrus, acidic fruit skin
Pulp from the juicer
Tea leaves/bags and coffee grounds
Hair, vacuum cleaner dust, soiled paper, tissues
Shredded moist newspaper & cardboard
Paper towels, shredded egg cartons, toilet roll inners, paper lunch wrap
Lawn clippings in small quantities (spray free), weeds, clippings, prunings, dirt and leaves
Sawdust (untreated), wood ash
Spicy foods, onions, garlic, leeks, capsicums
Meat and dairy products
Bread, pasta and processed wheat products
Fats or oils
How much to feed the 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.
Remember the hungry bin is not the same as a rubbish bin. A garbage truck does not magically empty it every week! The worms cannot eat the food as fast as it is possible for you to put it in, especially if the population is small when you start. It is better to underfeed your worms than overfeed them.
A good rule of thumb is that uneaten food should be no more than 5cm deep. You can check this by digging through the top layer of the bin and checking how deep the uneaten food is. In a healthy bin finished castings should be present 5-10cm (2-4in) below the top layer. You should also be able to see a mixture of adult and juvenile worms, indicating that the worms are breeding. If uneaten food is building up, simply stop putting new food into the bin until the worms have eaten the food present.
Approximately 20cm (8in) below the surface the food should have been completely converted into worm castings. Finished castings look like high quality compost and have very little smell.
Worm eggs should also be present in the castings immediately below the food layer; signifying conditions are ideal for breeding. The worms need to be able to lay their eggs in fresh castings immediately below the food they are eating. If the bin is overfed and a layer of rotting food has formed, the juvenile worms will be unable to move upwards through the rotting layer to the fresh food when they hatch, resulting in the population declining.
To remedy a build-up of rotting scraps, you may need to gently fork a small amount of fibrous material (See FAQ 3) into the top food layer. In extreme cases the rotting food will need to be removed completely and the bin restarted, as rotten food can take a long time to break down in the bin.
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.
Generally you should not need to add water to the hungry bin. Food scraps have a high water content, which helps keep the bin moist. The design lets excess water drain from the bin, but ensures enough moisture is retained to maintain optimal conditions. The worms do need to be moist though, so if the bin has dried out, sprinkle a little water on the top of the bin. If you have added dry matter like shredded paper you may also need to add water. Take care not to drown the worms, the top should only be as wet as a wrung-out sponge.
The bin will produce about half a litre (one pint) of liquid a day when it has a full worm population and is fed regularly. It is important that the liquid is free to drain from the bin at all times.
If liquid from your bin is not collecting in the drip tray, it may be too dry. See Should I add water? above. The filter tray may also have become blocked with paper or plastic if this has been placed in the bin. Remove the floor and check the filter.
Check that the bin is not exposed to intense sun for long periods and move to a shadier spot if necessary.
The liquid fertiliser should be mixed 1 part with 10 parts water before being sprinkled onto the soil around plants.
How much Liquid should my Bin produce?
How to harvest castings
Should I add water?
Castings should only be removed when the hungry bin has become full to the top of the taper. Removing castings before the bin is full will affect how much food the bin can process. The hungry bin needs to be at least ¾ full of finished castings to work most efficiently. This is to ensure the finished castings in the lower part of the bin have been cured completely, and are fully compacted. When the floor is removed, the shape of the bin means only the castings in the bottom part of the bin will fall out. When the castings have been properly compacted and had enough time to consolidate, they are largely free of worms and clump together, making them easy to remove and handle.
If the floor is removed before the castings have become properly compacted, all the material present in the bin, including the worms, will fall out.
Some worms may be present in the castings. The worms can be easily separated from the castings by spreading them on the upturned lid, and placing it on top of the bin. The worms present will retreat from the light deeper into the castings and the top layer can be removed. The separated worms can then be tipped back into the bin.
Plants have evolved to uptake the nutrients created by worms – their castings are one of the most beneficial fertilisers for plants. Castings are pH neutral, so are very safe to use with all plants. Even a small amount of castings or liquid added to soil will improve the performance of plants.
They can be used in the same way you use compost, or heaped around plants. Pure castings may burn the roots of small plants if used undiluted. For use on smaller plants it may be necessary to mix the castings with other soil first.
Signs of a healthy Hungry bin
When the bin is operating correctly, you should notice the following:
Very little smell
Large numbers of worms including juvenile worms in the top layer
Good quality worm castings and very little uneaten food approximately 30cm (12in) below the top layer
The liquid draining from the bin should be the colour of strong tea with little or no smell