We raised nightcrawlers for years. IMO worm food is the way to go. A single tube lasts for forever, and you never end up with any nasty surprises like what can happen if you accidentally put too much decomposing food in for them and forget about it (of course I didn't do that dozens of times...). We were friends with a guy who could get us pesticide-free peat, and we used that for their soil, and covered the top in moist paper towels.