well rotted kitchen waste - vegetable material only. Throw in some moss, grass clippings and keep the soil moist (not wet). Do not over-do the kitchen waste or the moisture and make sure the container/s have drainage (but keeps the worms from getting out). You may need to do some experimentation to hit the right combo. Maybe try a few flats with different additives. My dad used to keep 2 wooden crates in a cool spot in the basement with nightcrawlers in them. He was very successful with raising them.