How long can a California Blackworm grow?

These worms are a freshwater Annelid of the Class Oligochaeta. The oligochaetes include earthworms and a group of related, mostly freshwater, species of annelids. Over 3000 species are known. Oligochaetes all bear setae (small hairs on their sides that help "ratchet" them through the soil), but the number of setae present is much smaller than in polychaetes (their name (Oligochaeta) means "few hairs"). Black worms (Lumbriculus variegatus) are also known as a California blackworms, or mudworms and are members of a small subgroup of oligochaetes that are not earthworms or tubifex. About 3 - 4 inches in length when relaxed, and on the reddish side (usually a brighter red than tubifex despite their name). Blackworms are found in the sediments of North American ponds and lakes. They do not like light, are thicker and more earthworm-like than tubifex, coil and thrash like redworms when caught, and do not form the slimy blobs common to tubifex when kept confined in large numbers.