So you are interested in worm composting and you already decided between red wiggler worms , European Nightcrawlers and African Nightcrawlers. Your next major question is "How many worms needed to start a worm bin?" and the answer is not a simple answer. The answer can be answered with three questions "How much worm food do you have access too?," "What size is your worm bin?,'" and "What is the intended use of composting worms?"
How Much Worm Food Do I Need
Compost worms eat roughly 25-35 percent of their weight per day. This is the consensus among academia research available however some places on the internet state much higher up to 100% of their body weight. Using the information above, one pound of composting worms will roughly eat 1.75 to 2.45 pounds of food per week and two pounds will eat 3.5 to 4.9 pounds of food per week.
What the Size of My Bin?
The ideal number of composting worms are 1-2 pounds per square feet of bin surface area and not volume. Okay, by now you are thinking about your days in high school math class, so area is simply width x length. Example: bin is 1.5ft (18 inches) by 2 feet (24 inches) your surface area is 1.5 x 2 = 3 sq ft. I would recommend starting with 3 lbs of worms.
What's My Intended use for worms?
If your ideal use of composting worms is worm casting production, I would recommend two pounds per square foot. On the other hand if you want to save money and grow out your population of worms, I would recommend one pound per square foot. Once the worms reach optimal population, the worms will self regulate their population.