depending on where you got it from its most likely broken down newspaper and a mixture of a vegetable compost such as mushroom compost. its cheap and worms break it down eagerly. it should be fine. but it'll turn into castings when they are done breaking it down anyways.. so it might just go back to that unwanted ddirt lmfao
there isnt really anything wrong with feeding newspaper. if you are afraid if what you feed your pets you should see what companies feed your livestock. as long as the newspaper isnt glossy, you are fine. try to keep it black and white though. you can use peat, but it wont affect the ph of water. it'll affect your garden.
well, i gotta say, the worms are still alive and its been awhile now. im only feeding 2 rays so the last batch of worms that came in dirt would be white and moldy by now BUT the substrate in with this batch has kept them alive and healthy MUCH LONGER! Just thought i would give an update!