This type of worm farm has many benefits really!
- It's easy to make
- You can get hold of tires easily
- You can stack your system in levels
- You can easily access your worm wee to make excellent fertilizer
- It's rock solid, so animals and weather won't hurt it.
- You can make more cheaply as your worms multiply
The lid could also be heavy hessian bag to allow rain to flow through and more oxygen. In cooler regions you may want a lid.
You may also want to consider using a plastic drum underneath to catch the worm wee.
Also, I would flush the system for a week before adding the worms to remove any nasties that may hurt your worms.
Basically, if your only starting off with 1000 worms 2 tires are only need.
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ps: This photo was sourced from http://epilogist.wordpress.com/2012/03/20/tire-worm-farm-diagram/