Vinegar Eels (Tubatrix aceti) are harmless, non parasitic nematodes, that many tropical fish keeping breeders feed to smaller fry when larger microworms and baby brine shrimp or smaller infusoria cannot be used.
Many tropical fish keeping enthusiasts prefer feeding vinegar eels to smaller fry instead of microworms because of their ability to live in freshwater for extended periods.
Their enticing wriggling action as they swim in the water column makes vinegar eels a preferred food for many mid water fry species. Instead of dropping to the bottom of the tank and quickly dying off like microworms, they can survive for over a week in a freshwater aquarium environment.
Vinegar eels are super easy to raise. All you need is a glass jug, vinegar, water, some food, and a starter culture.
Fill a one gallon glass jug almost to the neck with a 50/50 mixture of apple cider vinegar and water. Add 4 or 5 marble size pieces of apple along with your starter culture to the jug, cover with a rubber band over a small piece of cheesecloth, and set the jug aside in a dark location.
After a couple of months when you can see a light colored cloud of worms congregating at the top of the culture, the vinegar eels will be ready to harvest.
Below is another one of the many alternate methods for culturing and harvesting vinegar eels:
Although harvesting takes a little bit of effort, it does not require much time. You will need a food baster, a small jar for the vinegar eels, a small funnel, and some fine coffee filters.
Make a small sieve by placing a coffee filter into the funnel.
Use the baster or a siphon to remove some of the cloudy liquid from the jug and filter it into the small jar. Repeat until you have enough vinegar eels in the filter to feed your fry.
Pour the vinegar solution back into the culture, rinse off the eels that you filtered out of the culture with some fresh water, and transfer them into another jar filled with fresh aquarium water by reversing the coffee filter in and swishing it around a bit.
You will be able to see plenty of vinegar eels swimming around in the jar ready to be fed to your fry. Just pour as many as needed into the rearing tank.
Unlike white worm, micro worm, and other cultures that “go sour” after some time, a vinegar eel culture can last more than a year without any special care.
Start a couple of cultures for a backup and you should have enough to take care of as many small fry as you can possibly breed.