This is no ordinary worm farm: it is a fun project to do with the kids, it works like the best of farms, it looks fantastic and… it doesn’t cost any money!
Here’s how to make it:
1. Get three polystyrene boxes from your local fish shop / market / green grocer. The boxes should all be of the same size, stackable, in good condition, and preferably white (mine were printed; it wasn’t the end of the world, just required a little extra work). One of them needs to have a lid.
2. You need to drill some holes on the boxes. The first box (which will always be at the bottom) needs one hole to let the juice out. A diameter of 2-3 cm will be perfect.
If you don’t have a drill, don’t worry: polystyrene is soft, you can cut the hole with a knife, scissors, or any other hand tool you can find (it doesn’t matter if the hole doesn’t look perfectly neat, just make sure it doesn’t crack to the sides).
3. The other two boxes need lots of smaller holes on their bases. Again, a screwdriver can do the job if you don’t want to use a drill. For these holes, a diameter of 5mm will do. Mine are larger than that, and they are OK too.
4. If you have children, this will be their favourite part: time to decorate! Think of a simple theme, sketch it on a piece of paper first if you want, and have fun colouring! I recommend acrylic paint, as it is water-based and won’t damage the polystyrene. Don’t even try to use oil paint or any other solvent-soluble paints — they will destroy the boxes.
Mind you, painting on polystyrene is not easy. The material is porous and it is very hard to paint fine details, so unless you are an accomplished artist I suggest you stick to a simple design. Also, you can’t draw on polystyrene with a pencil. The lead will just mark a fine groove on the material which, of course, you won’t be able to erase if it doesn’t look right — another reason to keep it simple.
My boxes had a blue print on the sides. I covered it with two coats of white acrylic and let it dry before applying the final "artwork".
When you plan the design, keep in mind that the bottom box will always be the ground floor, but the other two will take turns at being first and second floors.
Here is the finished Mansion (right).
5. Once the paint is totally dry, you can start preparing the middle box to receive its first guests. First, cover the base with one layer of newspaper
6. Fill up with moist soil (ideally, organic potting mix with some compost) up to a height of 10-15cm, uncompressed. Then add some composting worms. You don’t need a lot of worms to get started. I got a handful from a friend and that was enough to get going. A few days later, another friend donated some more. With the right conditions (temperature between 15Cº and 25ºC, good air circulation, good moisture and enough food) the population doubles in 40 days.
7. It is generally recommended not to overfeed the worms. If there are some food scraps in the container the worms came in, let them settle down for 24 hours before adding any more food. Spread them out a bit, so the scraps form a thin layer on the surface rather than a ball, cover with a hessian bag (or any woollen or cotton rag), put the lid on, and let the worms get used to their new home.
8. The Worm Mansion needs to be elevated so that the liquid collected on the ground floor can fall through the hole into a bucket. Crates can be handy. Use a small rock or object under one crate to create a slight incline to ensure that all the liquid is directed to the hole, and it doesn’t remain stagnant inside the base box.
9. For now, the Mansion can work as in the picture above, with two boxes only. When the first floor fills up, you will add the Penthouse (below).