Answer: The preferred worm for composting is the red wiggler. I think you'll have better luck if you use a special "worm bin" designed for this purpose. These are large bins with various levels. You add vegetable scraps, and the worms go to work decomposing them. You can them remove the compost, or draw off the nutritious liquid for fertilizing plants. You can keep a worm bin going year round by bringing it indoors in the winter.
Although nightcrawlers can be found in and around compost piles, they are generally not considered to be the best composters, because they tend to "travel". (However, they won't be able to go far on your balcony!) In regular compost piles, the decomposing is mostly done by naturally occuring bacteria, and less by earthworms.
For more information about worm bins, visit National Gardening Associations Kids Gardening web site at http://www.kidsgardening.com
I hope this helps!
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