White worms are real easy to culture. I use a small box with garden soil and introduce the culture. Feed the culture bread soaked in cold water. Cover the bread with a piece of glass. Keep the box in a dark cool place. When the bread is gone replace it. When the food is introduced the worms come up to feed. Just scoop them up and drop them in the tank.
I've had my culture going for about 3 years now.
Joe