Using the wrong type of limestone to correct pH imbalances can kill your worms. We reccomend Powdered Limestone to correct the pH. Other forms of limestone will burn your worms. You should wet down your worm beds/bins and then sprinkle the limestone over the bed. Once the limestone absobs the water you should turn the limestone into the bedding. You should test your pH again and add lime as needed until your pH is right. Just use a pinch at a time for a light sprinkling over the surface of your worm bed. One pound will last a long time if you have a compost bin or two.
If you cannot find powdered limestone you can get it here. We sell our limestone in 1 pound bags. Shipping via USPS Priority mail is included in the price!