This worm bin project has been one of the most enjoyable (and luckily successful) garden experiments I've ever taken on! And after a bumbling attempt at bin migration last time , I finally got it right! It seems that you have to wait until both bins are full to harvest the castings from the bottom bin, otherwise you leave too many worms behind. So after separating the bins, here's my prize-a bin full of rich worm castings (a.k.a. poop! :)
here , and it was really easy! You can certainly spend the $100 or so for a pre-made bin, but making my own was much more satisfying.
websites , this liquid is called "leachate", and not as good for plants as "castings tea" (but my plants didn't read this). I water my houseplants with this leachate and they seem to really enjoy it. Hey, the proof is in the results!
If you've ever wanted to build your own bin, I say go for it! It's fun, easy, and educational for children ("vermicomposting" is a great science project). There are lots of great resources on the web, and I'm always happy to help in any way I can as an "experienced" worm-wrangler. (I've had this bin going since 2006 with just a few startup "blunders" :)