(A simple guide for live food lovers)
Vinegar eels are one of the easiest live foods you can culture for your fish. They’re tiny, wriggly, and absolutely perfect for fry and small species like guppies, bettas, and tetras. Best of all - they practically grow themselves once you set them up right!
What You’ll Need
1 clean beer bottle or similar glass bottle
Apple cider vinegar (with the mother is best)
Fresh dechlorinated or RO/DI water
1 small apple slice (optional, but speeds things up)
Filter wool or a small wad of cotton wool
A turkey baster, pipette, or airline tubing for harvesting
A spare container or bottle for splitting the culture later
Mix the brew:
Combine half apple cider vinegar and half fresh water (use RO/DI if possible - not tap water with dechlorinator). Fill the beer bottle about ⅔ full.
Add the apple:
Drop in a thin slice of apple. This gives the vinegar eels something to feed on as the vinegar ferments and bacteria grow.
Introduce your starter culture:
Pour in a small amount of vinegar eel starter culture from an existing colony or a supplier.
Cover the bottle loosely:
Use a paper towel or cloth secured with a rubber band. The eels need air, but you don’t want fruit flies moving in.
Leave it alone:
Keep the bottle at room temperature (around 20–25 °C). Within a week or two, you’ll notice a cloudy layer of tiny moving eels near the top of the bottle. That’s your colony thriving!
Harvesting Vinegar Eels Using a Beer Bottle
Here’s the easy “beer bottle and filter wool” method:
Set up a harvest bottle:
Take a clean beer bottle and pack a small amount of filter wool into the neck.
Add vinegar eels:
Pour some of your eel culture into the bottom half of the bottle (below the wool).
Add fresh water:
Carefully pour fresh water (RO/DI or dechlorinated) on top of the wool until the bottle is nearly full. The eels will slowly swim up through the wool into the freshwater layer.
Wait 6–12 hours:
The top layer of fresh water will be full of eels ready to feed to your fish.
Harvest and feed:
Use a pipette or baster to draw from the freshwater layer and feed directly to your fish or fry.
Maintaining & Splitting Your Culture
To keep your vinegar eel colony healthy long-term, split it once a month:
Prepare a new bottle with the same mix - half apple cider vinegar and half RO/DI (decorated) water, plus a small apple slice.
❗ Important: Don’t use water treated with chlorine remover. The chemicals can upset the delicate bacteria the eels rely on.
Add a small amount of your old culture to the new bottle to seed it.
Let it establish for a week or two before harvesting from it.
By rotating cultures monthly, you’ll always have a fresh, thriving supply of vinegar eels ready to go.
Feeding Tips
Vinegar eels can survive in freshwater for hours, making them perfect for fry tanks.
Feed a few millilitres at a time - you’ll see your fish darting around happily snapping them up.
No need to rinse them - just avoid adding too much vinegar liquid to your aquarium.
Pro Tip
Keep two cultures going at all times. If one crashes (they can after a few months), you’ll have a backup ready to split again - no more waiting weeks for a restart!