Vinegar Eels make a good supplemental fry food, especially for very small fry that are not big enough to take microworms. Like Microworms and Walterworms, they are nematodes; however, they are smaller than either. They can also be maintained in VERY low maintenance conditions. Unlike Micros or Walters, They DO NOT require sub-culturing every couple of weeks. Basically, all you need is a glass or plastic container, (1/2 gallon or 1 gallon is supposedly best, but 2 liter is fine) a 50/50 solution of apple cider vinegar and water, and some chopped apple. For more detailed instructions, click here. They are not as prolific as Microworms or Walterworms, nor should they be used as the sole diet for more than a few days, but they are a great food to have on hand for those surprise batches of fry, or for fry too small to take microworms.