If your worm bin has been up and running for 6 months or more, it’s time to harvest some castings. This is a good opportunity to check your worm count, http://www.naturesperfectplantfood.com/2012/09/21/whats-your-worm-count/ look for egg sacks and replace bedding. There are two main methods for separating worm castings from worms. Bribery which speaks for itself, and creating a hostile environment. If all you want to do is remove worms, bribery is very useful. Simply deny food to the worms for a week then offer them something delicious. A frozen then thawed apple works great or part of a melon. No need to freeze the melon. By the next day most worms will have congregated under the fruit, all you have to do is scoop them out. This however will not harvest any vermicast.
The first step in the next method, creating a hostile environment begins in the bin. Stop feeding your worms, this allows any semi-composted food to be consumed. Wait between 7 -10 days checking every few for moisture content. The castings should be moist enough to form a clump when pressured but dry enough to break apart with a finger poke. Once the food is gone and the bin sufficiently dry you may begin.
Separating worms from castings is a fairly time-consuming duty so make sure you have space reserved for a day or two. Worms will attempt to flee a hostile environment be it too dry, wet, hot or cold. They also avoid light and a combination of these conditions will force them together. Take a large flat service like a big tray or table top and remove a few litres of material from the bin, worms and all. Form it into a mound in the center and leave them alone for 10 to 20 minutes. Direct sunlight works best but any bright space will do. When you return the worms will have burrowed toward the middle of your mound. Scrape off the vermicast, don’t forget to look for eggs. http://www.naturesperfectplantfood.com/2012/05/18/red-worm-eggscocoons/ Repeat this process untill your left will a ball of worms. You can finish the bin or harvest as much as you choose. Do not leave the worms unattended in the night, they’ll use the cover of darkness to escape the harvesting surface or they may become dehydrated and die. Replace the bedding and start anew.