Worms can safely live in habitat with a fairly wide pH range, when you consider the pH of food material alone it can be very low or more acidic like tomatoes that come in at the 4.5 or avocado which runs about 8. Cattle manure, which is our main food source is more or less neutral never registering below a pH of 6 and usually around 7. That’s thanks to the digestive system of the cows. Worm cast or vermicast always has a neutral pH again thanks to the worms digestive tract.
pH plays a big part in soil productivity but not so much in your worm bin. You can manipulate the pH of your bin by adding eggshells which are almost entirely made of calcium carbonate a strong base that over time will lower the pH making it less acidic. The acidity of a bin will naturally rise and fall with vermicomposting action as the Nitrogen cycle continues breaking down organic material to feed your worms.