Although worms exist all around us, not any old worm is recommended for composting. Most compost enthusiasts recommend red worms. If you go out to the nearest city park or bait shop in search of worms you may end up with the wrong type of worms for a compost bin. Most worms fall into two categories. They are anecic and epigeic worms. Red worms are epigeic worms, while nightcrawlers are earthworms you dig from soil are anecic worms.
Anecic worms are known as earthworms because they are soil-dwelling worms. These types of worms tend to be solitary and create burrows to live in. An anecic worm burrow may extend as deep as 6 feet into the earth. This makes them unsuitable for compost bins, where many worms live in a confined area. If you put anecic worms in a worm farm bin, the overcrowded worms will attempt to crawl out of the bin.
Epigeic worms, such as red wigglers, are more desirable for compost bins because they dig lateral burrows in the first few inches of topsoil. The epigeic worms have no burrowing ability. Instead they prefer to live in loose organic topsoil which is easier for them to move through. Epigeic worms primarily feed on organic material, which makes them perfect for a compost bin. By some estimates, an epigeic worm will eat half their weight in food daily.
Finding the Right Worm
Many compost bin owners purchase red worms from vermicompost supply retailers. This is the easiest method to obtain red worms. Less expensive methods include obtaining worms from other compost bin owners and digging them up. Red worms may be found around an outdoor compost pile where soil is loose and full of organic litter that red worms prefer. Unlike nightcrawlers, red worms do not have a flat tail with tiny hairs on it. Nightcrawlers and other anecic earthworms use this tail as an anchor to make them harder to pull out of the ground.