“I see there are many manufactured plastic worm farms, the stackable style. I have access to as many five gallon plastic buckets as I want, do you know the diameter holes that are put in these stacks for the worms to migrate through to the next higher level? If I knew this, I believe I could build my own for almost nothing.” ~ Timothy Bonner
Yes it is a great idea to make your own stackable wormery. It may not look the best in the house, but if you keep it outside in the garage or in the garden, it certainly is a very cheap way of starting your first wormery system.
For new readers, the stacking wormery is vertical system consisting of multiple trays. Each try has a perforated base which allows worms to migrate through.
The system will start in the bottom tray. One the composting process is finished, waste can be added to the tray above and the worms will start to move up to the next tray in search of food. As a result the worms will be separated from the casts.
Back to timothy’s question, there is no definite size of holes to be used. In commercial wormery systems, I have seen holes as small as 2-3mm to holes over 1 cm. Worms are very flexible creatures and they naturally stretch and expand to travel to different places. When they stretch their bodies can be really thin fitting into gaps as small as 1mm.
Although larger holes will make it easier for worms to pass through, you also need to consider that the contents do not fall through easily. As the bin is piled up with organic waste, the processed cast in the bottom will more or less compacted together making it less likely to fall through the perforated holes, but if the holes are too big you will lose a lot of your cast when it drops through.
In conclusion, holes between 2mm to 5mm will be the best for a worm farm.