Vinegar eels are a common first food for betta fry and many other fish. They are smaller than most nematodes, last longer in the tank, and swim throughout the water column which prevents too much bottom-feeding.  They are extraordinarily easy to keep and can thrive for years with minimal attention. Vinegar eels, in my opinion, are a must-have food for all betta breeders.  While other cultures might crash or brine shrimp hatches might fail, you will always be able to pull out vinegar eels and know they are ready to harvest when you need them.

Eels collected at the top of the bottle

Culturing Directions:

What you need:

  • Jar or large bottle (1-2L) with a cap or lid.
  • 1 small apple, cut into slices small enough to fit into the jar
  • Apple cider vinegar (with or without the “mother”)
  • Treated tap water
  • Starter culture of vinegar eels taken from an established culture


  • Fill the jar with a 1:1 ratio of apple cider vinegar and treated tap water, leave a little space at the top for air and also make sure to cut a small air hole in the top of the jar.
  • Wash the apple thoroughly to remove any contaminants on the skin. Cut it into pieces and stick into the jar with the diluted vinegar.
  • Add the starter culture to the jar
  • Seal and store at room temperature. A dark cabinet is preferable but not necessary

(Note: Some people add a small pinch of sugar or yeast to their cultures to start them. I’ve never tried this myself and find it an unnecessary step. The apple will act as food for the culture).

I split my cultures and start fresh cultures every 6 months or so, sometimes letting it go as long as a year between splitting. In that time, I do not add any food or fresh water/vinegar to the culture.  The colony thrives well on its own. If you notice it getting cloudy it’s probably time to refresh the culture. To refresh, simply get a new jar and pour half the culture in there and then top both jars off with fresh diluted vinegar. If you don’t want to start a second culture but merely keep one going you can always pour half down the drain or offer it to another hobbyist then refresh the original with diluted vinegar.

Depending on the size of your starter culture you should find your culture ready to feed in about 2-4 weeks, sooner if you buy a large starter. If you have good eyesight or a magnifying glass you will be able to see the eels swimming around in the jar, if you cannot see them a ready to feed culture will look just the slightest bit cloudy when teeming with eels.

A new culture (left) vs a ready to feed culture (right)

Harvesting Directions:

There are two different methods to harvest vinegar eels. I call them “the easy way” and the “time-wasting” way.

The Easy Way:

  • Find a bottle with a long neck (preferably a clear one). A glass soda or beer bottle (rinsed well) works.
  • Fill the bottle up to the bottom of the neck with the vinegar eel culture, just to where the neck starts to narrow. (See photo)
  • Add a cotton ball or filter floss (available at most pet stores) to the neck of the bottle so that it is touching the VE culture but not submerged more than half way into the culture. Make sure that you pack the floss so that it fits tightly into the neck of the bottle. Also, make sure not to poke it down so far that you will not be able to remove it later.
  • Once the filter floss has been placed, fill the top of the bottle with tank water or treated tap water.
  • Stick a light over the bottle and wait. The eels will swim up through the filter floss into the fresh water. I generally set this up overnight and let the eels collect at the top of the bottle during the night then harvest them the next day.
  • Once a sufficient amount of eels has collected at the top of the bottle, simply take a pipette or eye dropper and suck the water from the top of the bottle and squirt into the tank. The filter floss prevents the vinegar from mixing with the fresh water at the top of the bottle so rinsing the VE is not required.
  • If you are planning to feed from the culture daily, you can refill the fresh water to the top of the bottle daily without needing to start over again. If using for more than 1 week I would suggest putting a piece of apple into the bottle during set up so that the eels have food. I generally set my bottle up just for a week at a time then remove the filter floss and return the remainder of the culture back to the mother culture since by that time betta fry are usually ready to move onto baby brine shrimp and other larger foods.


The Time-Wasting Way:

  • You will need a paper coffee filter, funnel, turkey baster, tank or treated tap water, and a cup.
  • Place the coffee filter in the funnel.
  • Using the turkey baster suck some of the culture out of the jar.
  • Filter it through the coffee filter and allow the vinegar solution to flow back into the jar.
  • Next, rinse the VE with fresh water. Do not allow the water to go into your mother culture.
  • Once the eels are rinsed, invert the coffee filter into the tank and swish it around or invert it into a cup of tank water, swish, then pour into the tank.

The reason I call this the “time-wasting” method is because you must follow these steps every time you wish to feed the VE to your fry. Using the bottle method, you can simply set up once, refill the top with water daily, and feed directly from there. Whichever method you choose, you will find vinegar eels an easy and cheap culture to keep around.