Limestone solves many problems encountered in a worm bin and seems to increase worm reproduction rates.
Used in your garden it helps provide plants with needed minerals and increases availability of fertilizers to plants. According to the manufacturer,
"Limestone, is a natural soil amendment which helps enhance the “living soil”. Just as you lawn needs food (fertilizer), it also needs vitamins and essential minerals like calcium and magnesium found in limestone. By incorporating Lime into your Lawn Care Program your lawn will better utilize fertilizer treatments."
Limestone helps in the worm bin by providng worms with calcium needed for worm health. Regular dusting of the bed surface with pulverized limestone will help prevent problems from beginning. These problems include mite infestations and sour crop. Use pH litmus paper to see if you may need to add limestone to your worm bed.