Red Wigglers are by far the most popular choice of composting worm for a lot of reasons. Firstly because they can tolerate a wide range of temperatures, unlike African Night Crawlers. Secondly, because they are top feeders making them ideal for modern multilevel worm farms available at most nurseries or build your own.
Worm castings are an organic form of fertilizer produced from Red Wiggler worms. Also known as vermicast, worm castings are essentially worm waste. As these worms eat through compost, their waste creates an optimal soil en-richer full of highly active biological bacteria and enzymes.