I kept mine in the aforementioned "growing tower". Each drawer is only 2" deep, and I kept about an inch of bran in each one, with a slice or two of potatoes thrown in once a week or so.
I found I could raise a lot more worms in shorter drawers, because growing worms in deep tubs which only contain 2-3" of bran just wasted a lot of space. The only time I ever had escapees was once when I left a drawer open and an egg carton sticking out of it and leaning against the drawers above it (I'd put the egg cartons in when I was going to change bran or wanted to harvest the worms, because they congregated under the cartons). Other than that brain-fart, it was a perfect high-intensity worm ranch
I found I could raise a lot more worms in shorter drawers, because growing worms in deep tubs which only contain 2-3" of bran just wasted a lot of space. The only time I ever had escapees was once when I left a drawer open and an egg carton sticking out of it and leaning against the drawers above it (I'd put the egg cartons in when I was going to change bran or wanted to harvest the worms, because they congregated under the cartons). Other than that brain-fart, it was a perfect high-intensity worm ranch