Vinegar eels (Turbatrix aceti) are free-living nematodes that thrive in highly acidic environments, such as unfiltered vinegar. These organisms are not true eels but translucent, microscopic worms typically measuring one to two millimeters in length. They are primarily cultured as a live food source for the smallest fry of aquarium fish, including bettas, killifish, and rainbowfish, which require minute, wriggling prey.
The Biological Diet of Vinegar Eels
The sustenance for vinegar eels comes not from the acidic liquid itself, but from the microbial film that develops within the culture. These nematodes are grazers, consuming the community of yeast and acetic acid bacteria that form the “Mother of Vinegar” (Mycoderma aceti). These bacteria, often Acetobacter species, convert alcohol into acetic acid, creating the necessary vinegar environment.
The eels are considered bacterial feeders, relying on the continuous growth of this biofilm for their nutrition and rapid reproduction. Commercial vinegar is typically pasteurized and filtered, removing this microbial community, which is why vinegar eels cannot survive in most store-bought products.
Creating the Ideal Culture Medium
To sustain a healthy vinegar eel population, the culture medium must promote the growth of their food source. A common mixture involves diluting unpasteurized apple cider vinegar with dechlorinated water, often using a 50% to 50% ratio or a slightly stronger 2:1 dilution. The resulting acidity typically falls within a pH range that the eels tolerate well.
The culture requires a nutrient source to feed the yeast and bacteria. This is commonly provided by adding a small piece of raw apple or a few grains of organic material, which encourages the necessary growth to form the food film. Maintaining a loose cover is necessary to allow for gas exchange, ensuring the microbial film receives the oxygen it needs to flourish at the liquid’s surface.
Survival and Feeding Behavior
Vinegar eels possess a complete digestive tract, and their feeding is specialized to their microbial diet. As grazers, they use a specialized mouth spear, known as a stylet, to pierce the cell walls of the yeast and bacteria. They then consume the contents of these microbial cells.
These nematodes are exceptionally hardy, showing tolerance for a wide range of acidity, surviving in solutions with a pH as low as 1.6. They reproduce by giving birth to live young, with females capable of producing up to 40 offspring in a single reproductive cycle. They can survive for months in a dormant state if their active food source temporarily diminishes.