From my favorite worm expert Kelly Slocum;
Worms derive their nutrients from the bodies of microorganims that decay organic materials (OM). Once the OM has begun to rot it softens or fragments into small pieces that the worm can take in to its small mouth. Once in the gut the worm digestive process selects the microorganisms living on and decaying the OM as its nutrition source. The OM itself is moved on down the intestine where it is reduced by a different group of bacteria and fungi that live in the worm gut, then wrapped in a mucous coat and passed from the body as a cast.
Vermicomposting systems are specifically designed to receive regular inputs of raw OM, (we typically refer to this as feedstock) which keeps the microbiology in the system at very high levels. Bedding materials in the bin are tyically high in carbon; things like shredded leaves, paper, cardboard and straw, and this carbon is balanced by the relatively high nitrogen in the food scraps or manure we add to the bin as feedstock. When the carbon and nitrogen are balanced there is an ideal source of nutrients for the bacteria and fungi pivotal to the worm diet, and their populations bloom in response. When microbes bloom, worm activity is optimized.
Let's debunk this myth that worm castings are bad for worms. Worms need the most biologically active environment they can find in order to grow at maximum. The cast of the worm can be as much as six times MORE biologically active than is the OM they ingest. As such, castings are beneficial in the system since they increase the microbial activity. In fact, worms will reingest their own castings over and over again, even in the presence of a rich food source. Some of the most productive worm beds in the world are maintained by removing castings just once per year. Now, having said that, castings can also be very dense. If you get a castings build up low in the bin it can sometimes restict air movement. You'll want to watch bin conditions and, if you find the worms are reacting to low O2 levels, clean out the castings.
Be very aware that the internet is loaded with overly complex and outright WRONG information about how to grow worms. This is not a complex issue and worms in nature do it without all the gyrations some humans seem to feel is necessary to aid them.
Are you being impatient? I would be shocked if you were exhibiting the patience necessary for vermicomposting! :: None of us, when we first began our foray into worms, was patient, and some of us have never gotten over our impatience! You're being normal, which likely means you are expecting a bit too much a bit too soon. Do relax a bit about the little buggers and enjoy the process. And remember, Worms thrive on five things:
Air
Water
Decaying organic matter (OM)
Time
Neglect
Kelly S