Tiny worms in the vinegar

The short answer Throw it out

Throw it out. They're vinegar eels, tiny worms. The FDA considers a finished vinegar that has them adulterated, and Fervida throws it all out, mother included: a house rule.

Reviewed October 26, 2026 · 14 facts, each with its source

When in doubt, throw it out. Fervida can’t see your jar. No page can tell you something is safe: it can show you how to look.

What you see

Tiny worms, thin as threads and almost see-through, wriggling in the vinegar. They're easiest to see if you hold the jar or bottle up to the light, especially near the surface and the mother.

Why it happens

They're vinegar eels: tiny worms that live where vinegar is made. There's some information that they help make it, which is why the FDA, the US food agency, doesn't treat them as a problem in a plant's tanks as long as the filtering works.

Finished vinegar is another matter. The FDA considers it adulterated, because it contains a filthy substance, and a single eel in a bottle is enough.

None of our sources explains how they get into a jar at home.

What to do

Throw it all out

Throw out all the vinegar, the mother too: don't keep it for another batch. Filtering isn't enough. That's a house rule: the FDA allows none in finished vinegar, and at home there's no way to check that the filter caught them all.
Wash the jar, the spoon, the cloth and everything that touched that vinegar in hot soapy water, and rinse well.
Sanitize it before you use it again: soak it for 20 minutes in water with 2 tablespoons of bleach per gallon. Use plain bleach, with no scent or detergent.

How to make a clean vinegar

No source says how to keep them out at home. This is what the guides call for to make a clean vinegar, and it's what Fervida's recipes do:

Start with a store-bought mother, a pure culture, or one from an earlier batch with no eels.
Sanitize everything that will touch the vinegar.
Cover the jar with a cloth held on with a rubber band: it lets air in and keeps insects out.
When it's ready, filter it through several layers of fine cheesecloth or a coffee filter, and pasteurize it at 60–71 °C (140–160 °F) for at least 30 minutes.
Store it in capped bottles.

Where every figure comes from

Every statement on this page comes from a food safety guide. We keep a copy of each source and quote its exact words, in its original language.

1

There is some information that vinegar eels help make vinegar

“Because some information which indicates that vinegar eels aid in vinegar production”

U.S. Food and Drug Administration · CPG Sec 525.825 Vinegar, Definitions; Adulteration with Vinegar Eels (March 1995) · read on October 25, 2026
2

In a plant's tanks they aren't a problem, unless the filtering fails or they reach the finished vinegar

“we do not believe the finding of vinegar eels in a firm's bulk storage tanks or generators should be considered as an objectionable condition unless the firm's filtration system is not functioning or unless the eels are present in the finished product.”

U.S. Food and Drug Administration · CPG Sec 525.825 Vinegar, Definitions; Adulteration with Vinegar Eels (March 1995) · read on October 25, 2026
3

In finished vinegar they're objectionable: the vinegar counts as adulterated

“The finding of vinegar eels in finished product would be considered objectionable and would render the finished product adulterated”

U.S. Food and Drug Administration · CPG Sec 525.825 Vinegar, Definitions; Adulteration with Vinegar Eels (March 1995) · read on October 25, 2026
4

To the FDA, vinegar with eels contains a filthy substance

“it consists in part of a filthy substance by reason of the presence therein of vinegar eels.”

U.S. Food and Drug Administration · CPG Sec 525.825 Vinegar, Definitions; Adulteration with Vinegar Eels (March 1995) · read on October 25, 2026
5

A single eel in a bottle of finished vinegar is enough

“Actionable if finished vinegar in consumer-sized bottles contains any vinegar eels.”

U.S. Food and Drug Administration · CPG Sec 525.825 Vinegar, Definitions; Adulteration with Vinegar Eels (March 1995) · read on October 25, 2026
6

Wash the jar and everything you use in hot soapy water, and rinse well

“Wash all surfaces and containers that will be used with hot sudsy water and rinse well before use.”

K-State Research and Extension (Kansas State University) · Taking a New Look at Fermented Foods (MF3491, June 2020) · read on October 20, 2026
7

Everything that will touch the vinegar, sanitized

“Everything that will touch vinegar should be sanitized.”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026
8

20 minutes in water with 2 tablespoons of bleach per gallon

“Soak everything for 20 minutes in a solution of 2 tablespoons chlorine laundry bleach to 1 gallon of water”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026

Show the remaining 6 claims

9

A pure culture of vinegar bacteria, the mother, is recommended

“It is recommended to order pure cultures of bacteria, sometimes called the mother of vinegar”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026
10

One batch's mother can start the next

“They can be used to start a new batch of vinegar, so it is not necessary to purchase new starter bacteria”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026
11

The jar covered with a cloth: it lets air in and keeps insects out

“Cover the container with a cloth to keep the insects out while allowing air to freely reach the stock”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026
12

To pasteurize, 60–71 °C (140–160 °F) for at least 30 minutes

“the temperature of the vinegar must reach at least 140°F and should not exceed 160°F and should be held at that temperature for at least 30 minutes”

NC State Extension · Vinegar Making (July 2022) · read on October 25, 2026
13

Once done, filter it through several layers of fine cheesecloth or a coffee filter

“When the vinegar is fully fermented, filter the liquid through several layers of fine cheesecloth or filter paper—a coffee filter works well for this.”

Ohio State University Extension (HYG-5346), republished by Penn State Extension · Making Cider Vinegar at Home (updated December 2025) · read on October 25, 2026
14

Once done, store it in capped bottles

“The vinegar is now ready for storage in separate, capped containers.”

Ohio State University Extension (HYG-5346), republished by Penn State Extension · Making Cider Vinegar at Home (updated December 2025) · read on October 25, 2026