Turbatrix aceti (Vinegar eels, Vinegar nematode) are free-living nematodes that feed on the microbial culture, called mother of vinegar used to create vinegar, and may be found in unfiltered vinegar. Vinegar eels are often given to fry (baby fish) as a live food, like microworms.
Although they are harmless and non-parasitic, leaving eels in vinegar is considered objectionable in the United States and is not permitted in vinegar destined for American consumers. Manufacturers normally filter and pasteurize their product prior to bottling, destroying the live bacterial and yeast culture that these nematodes require for sustenance. They are usually about 2mm long and feed on the bacteria from apples.