Vinegar eels are not eels at all, but are nematodes, a type of worm. They are very easy to raise, and the cultures will last a long time. I raise them mostly as a back up food for fry in case I don’t have baby brine shrimp or micro worms available.
Start with a gallon glass jug like the type they sell apple cider in. Fill it up with a 50-50 mixture of cider vinegar and water up to the point where the jug starts to narrow. Add in a half dozen chunks of apple about the size of marble. Dump in your starter culture and put it in a dark location for a couple of months.
At that time if you hold it to a light you will see a light colored cloud in the top 1/3 of the culture medium. To harvest you will need a turkey baster, a funnel, a small jar, and some coffee filters. You will need to experiment with different types of coffee filters. Some are too course and let the worms through.
Put the filter in the funnel and put the funnel in a jar. Use the baster to remove some of the clouded liquid from the jug and squirt it into the funnel. Let the liquid drain off. You can repeat this a few time if you need more eels. Finally pour some clean water into the filter to rinse them. Pour the vinegar solution back into your jug
When the rinse water has drained, you can swish the filter in a container of clean water. You can see the worms swimming in the water if you hold it up to the light. Just pour the worms into your fry tank.
Unlike micro worms that sink to the bottom of the aquarium, the vinegar eels will swim in the tank. This is great for tropical fish fry that do not go near the bottom to feed.
I don’t feed vinegar eels all that often because harvesting takes more effort than microworms. I keep vinegar eels as a back up in case my microworms are not producing and I have fry that need live food. A culture will last more than a year and does not require any care. I usually start a new culture in early January each year.