Home Grown Food - Vinegar Eels

Posted by Aquatropic Staff on September 18, 2023

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If you google the term “Vinegar Eels,” most of what comes up is people panicking on forums about what is wriggling in their home-made vinegar or kombucha, or articles about how to deal with this. What is wriggling in their food is a harmless, free living nematode called Turbatrix aceti. They were first discovered (or maybe just noticed) in 1656 by Pierre Borel. They feed on the microbes in natural vinegar cultures (the thing you use to make vinegar is called “mother of vinegar”) this is a fun experiment but has little to do with our fishy hobby.

What does have to do with this fishy hobby, is that these nematodes make excellent fish food for baby fish that are too small for baby brine shrimp or microworms. When baby fish are eating infusoria, vinegar eels are an excellent additional food. They are ideal for feeding to freshwater fry as they can live in freshwater for as long as they can find bacteria to eat, and they like to stay swimming high in the water column, thus being available for consumption! So while overfeeding is still something you should avoid, it's less likely to cause issues when feeding a live food that can continue to live in the environment that it is getting fed into.

Another benefit to feeding vinegar eels is how easy they are to culture. While they are not as fast to raise as many of the other home grown foods we've covered here, the cultures of them are extremely durable, long lasting and incredibly simplistic.

To start out, you only need a few things. First you need a jar, and we suggest this be glass, have a lid, not too big and be easy to clean; things like pickle jars are perfect. In a pinch you could also use plastic containers like those used for liquid take out. It will help if the container is clear so you can monitor growth in there more easily. Vinegar eels will move toward light, and with a clear container, you can put a small flashlight (or the one on your phone) up to the side of the jar and see the little wigglers swim that way.

Next, you need a mix of water and vinegar. Water should be dechlorinated, but not from your aquarium. We suggest using bottled spring water or the like. The vinegar part should be apple cider vinegar, it can be as cheap or as nice as you want. Most of the apple cider vinegar for sale has been filtered and pasteurized before bottling so they won't carry any live nematodes with it. We've done this culture with a few different blends of water and vinegar, from as low as 25% vinegar to full vinegar and we've had better luck with at least a 50/50 mix of water and vinegar. Higher concentrations of vinegar worked fine, but weren't noticeably better. Dirk Schulze-Makuch Louis Neal Irwin, in their book “Life In The Universe: Expectations and Restraints”, call Turbatrix aceti “likely the most pH tolerant multi-cellular organism.” They can allegedly live in a absolutely massive range of pH, from below 2 to almost 11, both ends of this spectrum are intense enough to kill just about anything else; for reference, bleach is in the 11 range and sulfuric acid is about 1. With this in mind, it's clear that strong concentrations of vinegar (even full vinegar) will not deter the nematodes but will deter several other possibly competing organisms.

Lastly you need an apple. An organic apple or even better, one from the tree in your yard would be perfect. You are trying to avoid pesticides on your apple. Crab apples work amazing for this. Gently wash whatever apple(s) you chose and if you are using a full size apple, cut it into eight slices or more. If you are using crab apples, cut them in half. Add a single slice of apple (or 4 half crab apples – thumb sized) to the jar, and pour enough of the water vinegar mix over it to substantially cover (usually about a cup of liquid). In this step, you can also add a culture. If you've used a local tree apple, you won't need to, but it will make this process go faster. Vinegar eel cultures are available from a wide variety of sources. Some Local Fish Stores may have a culture, but they are also available from biological rearing sources. Do a google search for Turbatrix aceti cultures and you'll get more than a few options to choose from. Once you have an active culture, you can obviously use it to seed new jars.

Next we loosely close the jar to allow for oxygen transfer and then the exciting part happens. Actually no, that's a lie. Now is when we wait. Hence the need to seed multiple jars. This isn't a fast process. In our experience the culture will be harvestable in six weeks, and this is largely dependent on temperature. While the eels can live in temps that are lower or higher, you should keep them between 65 and 80 degrees, with a sweet spot in the middle of those numbers. If you can maintain them at 78, your harvest time will come sooner, if you keep them at 67, it will be slower. Vinegar eels are sexually mature after about a month and a few sources say they can live for up to ten months. Our experience is that the cultures need to be restarted every six months. With this being said, there are many stories around the internet about aquarists leaving these cultures ignored somewhere for time periods up to years long and the culture being okay.

Harvesting vinegar eels for feeding can be done in a few ways, and for years the most popular way was to pour the culture through a clean coffee filter. This process leaves you with a bunch of one or two millimeter long worms that still need to be rinsed of vinegar before feeding. Now we suggest using the long neck bottle method. You'll need a clear bottle, like a small flower vase, or a beer / soda bottle. Wine bottles will work, but they require a lot of culture because of their volume, so this may work better for those of you who chose larger culture vessels. Use a funnel and pour your culture into the new harvest vessel up to the base of the neck of the bottle. Add a couple cotton balls and gently push them down until they touch the vinegar mixture and expand from the liquid. Once they have expanded, gently pour clean water on top of the cotton balls to make a water layer above them. Be careful not to over pack the cotton balls, as we want the vinegar eels to migrate through them to get closer to the oxygen. The water and vinegar won't mix through the cotton ball, and the eels will swim suspended in water which you can remove with a small baster and feed directly to your baby fish! Then just add more fresh water and you can usually harvest the same bottle tomorrow. You should be able to repeat this at least a few more times.

Once you are done harvesting the bottle, you can use the liquid to seed new cultures. You can keep this culture around for a long time without it dying out. Just keep it topped off with freshwater when it starts to evaporate. We personally have never had one of these cultures go bad, and if you dedicate to re-culture every six months, we think it's unlikely you'll have one go bad either. Some people culture in their harvest bottles and this works just fine, they are just harder to clean and harder to get apples into. For those of you using smaller crab apples, this shouldn't be a problem.

For those of you who are interested in growing your own food, for rearing your own fish, vinegar eel culture is a nearly idiot proof way to add a live food to your baby fish's diets. While most of the foods we've covered in this series have been pretty easy, it's arguable that Turbatrix aceti might be the easiest one! Now hit up your Local Fish Store, and start planning what fish you want to breed!