Probably the most difficult task for the person doing home composting of worms is saving your worms when you harvest the compost. The compost contains many cocoons and very small baby worms which are difficult to see much less separate out to start a new box. I will describe my method which is used and described by many vermicomposters.
Step 1 - I dump the whole box onto a large surface such as a ping pong table. I protect the table with a sheet of plastic. The ball does not bounce well with the worms and compost on the table. Tell the kids they will just have to wait for a few hours to play ping pong.
Step 2 - I remove all the uneaten food and newspaper or bedding and put it into a large spackle bucket. Some worms and cocoon will be included with this stuff.
Step 3 - I make a number of conical piles using the composted materials. While doing this I pick up as many worms as I can and put them in a quart container with a little bedding to keep them happy.
Step 4 - I direct a bright light onto the piles. The worms hate the light and bury deep into the pile.
Step 5 - After about 1 hour, I return to the piles and carefully remove the outermost layer on each pile.
This compost is put into a plastic tub container about 6 inches deep. Again any worms found in this process are put into the quart container for the worms.
Step 6 - Step 5 is repeated for the next few hours until the piles are very small at which time most of the worms from each pile will be found clustered together. They can then be easily gathered and put with the other worms in the quart container.
Step 7 - I cover the compost in the tub with wet newspaper. I put a couple of banana peels under the newspaper to attract any worms remaining in the compost. I usually wait at least 1 month and collect the baby worms that feed on the banana peels. I usually get 500 - 1000 worms this way before I sift the compost in step 9. If you ignore this step, you will lose a large number of worms that could be working for you in the future. I find a sharp pencil works well when picking up the baby worms that accumulate around and on the banana peels.
Step 8 - The worms can be used for bait, starting new boxes, sales, or feeding other creatures.
Step 9 - I like to sift the compost before using or selling it. I use a 1/4 inch screen. When sifting I am always on the look out for worms which I save and put into one of my boxes.
Step 10 - I put wet newspaper over the uneaten food and bedding in the spackle bucket. Usually in time the worms from the material in the bucket will start eating and composting the remains. I just keep the newspaper wet, and they survive very well. In time the contents of the bucket turns to compost or it can be added to a new or existing worm box. Sometimes I even start feeding the worms in the bucket just like I do in the worm boxes. A top can be put on the bucket, but I usually find the damp newspaper works very well.
My procedure is not practical for worm farmers, but works well for me in my small operation. I would be interested to hear what methods other vermicomposters are using to separate their worms.