Out of all the worm species only a few are suitable to use in composting bins. The red wiggler (Eisenia) is the most popular as it has the characteristics useful to breading and growing worms. It is claimed that they will eat between 50% to here 100% of their weight a day. With their hearty appetites they then leave behind more castings. Their activity is usually within 6 inches of the surface. This makes feeding the worms and harvesting the castings a simple process.
Another reason the Red Wiggler is a popular composting worm is because they reproduce faster than many of the species. Since each worm is both male and female any two worms of the species can mate. How they decide the role each one should play I do not know. Maybe its who surprises who.
As the earthworms tunnel through the soil, the soil from the tunnel passes through their digestive system scavenging organic material and bacteria. The worm castings are of a ph that most plants thrive on (slightly basic -ph a little above 7). They contain nutrients from the organic material in the soil and a lot of bacteria. If in their tunneling the worms encounter harmful bacteria, by the time it passes through the worm’s digestive system it becomes beneficial bacteria. As an added benefit the worm castings are coated with a mucus membrane enabling them to hold moisture and slowly release nutrients into the soil.
One of the considerations of having your own worm bin is to duplicate the living and growing conditions they would thrive on in the open soil. Although there is a wide range of materials that can be used in the bin, worms do have their preferences. Bin moisture is essential. This is one of the most important conditions to control. To little moisture will make tunneling through the bin difficult for the worms and to much moisture will eliminate any oxygen from the bin and the worms cannot live. Two much water will also will tend to putrefy the bin materials and cause a smell.
Many worm growers suggest using a moisture meter to determine the correct moisture content especially until one develops a feel for the correct moisture content. Most of the worm farms selling worms and equipment tout how easy it is to raise worms. It really is easy once you figure out what to do and be consistent doing it. It is not unusual to lose the first batch of worms while you figure out what to do.
Bin can be constructed from a wide range of materials. Avoid having treated wood in contact with worm media. Chemicals detrimental to the worms could leach out. Most untreated wood will have a limited use as moisture present in the bin causes rotting. Using a wooden box for structural support and lining it with a plastic material would eliminate a lot of the wood rotting problem. Be sure to provide for effective drainage.