November 16, 2019

Open or Closed Lid for Water Kefir Fermenting?

Open or Closed Lid for Water Kefir Fermenting?

Last time we looked at the pros and cons of milk kefir fermenting with an open or closed lid. This time we look at water kefir.

Homemade water kefir can be fermented with either an open lid or a closed lid, or in other words, aerobically or anaerobically. Aerobic basically means a ferment with oxygen, which is done with an open lid. Anaerobic means without oxygen which is done with a closed lid or airlock. Most people traditionally use an open lid with water kefir ferments, but just like milk kefir fermenting, its becoming more and more popular to use a closed lid.

There is really no "correct" way as each has its own advantages and disadvantages. It really comes down to personal preference in the end.

But there are some very distinct differences in the bacteria and yeast and chance of contamination.


The biggest difference between milk kefir and water kefir is that water kefir usually does have larger amount of acidic acid bacteria. Sometimes water kefir will have a distinct sour vinegar flavor that’s a little like kombucha and other times water kefir will be more tangy without that vinegar bite. The difference is the acetic acid bacteria. That type of bacteria loves an aerobic environment (open lid) so if you love that vinegar flavor, having an open lid is a must. Otherwise try an anaerobic ferment instead

An anerobic ferment / closed lid ferment may decrease the acetic acid bacteira, but there are strains that do better without oxygen. Bifidobacterium is likely one of them. In one study, the reseachers show that an anaerobic environment increased the level of Bifidobacterium aquikefiri. Bifidobacteria in general helps digest fiber and carbs. They produce those important short-chain fatty acids and other important vitamins like vitamin B.


The one thing that people want with water kefir is fizz and more fizz. Carbonation and fizz is a by-product from the yeast during the ferment. So more yeast will naturally create more fizzy good stuff.

An open lid or aerobic ferment helps create more yeast and give it more potential for carbonation.

It’s quite confusing though because an open lid means that most of the carbonation escapes during the initial ferment. However, if you are looking to do 2nd ferment (which we recommend with water kefir), then that's where an open lid will excel. 

If you plan to drink the water kefir fresh or within 1-2 days and want carbonation, then an anaerobic (closed lid) ferment may work best.


One of the biggest benefits of anaerobic ferments is that it prevents any airborne contamination. Water Kefir is highly resistant and protective against mold, so that risk is usually really low. The risk of mold is lower than kombucha or milk kefir. It's possible that airborne yeast may contaminate the water kefir, but its likely that won't affect the ferment much and will just add some local yeasts to the brew.

The biggest risk is probably kombucha. If you ferment too close to kombucha, it may start develop its own scoby on the surface. It's not a health risk, but it can be annoying to deal with. A good rinse and rest in the fridge might help reset the gains.

Instructions on how to do an oxygen rich aerobic ferment:

  • The easiest way is to use a paper towel and elastic band. You can use anything that is porous enough to allow the free exchange of air without being open enough to allow fruit flies (and other bugs) in.
  • We offer a convenient elastic cloth lid that’s easy to wash that makes doing aerobic ferments easier and also make it look beautiful at the same.

How to do an anaerobic / closed lid ferment:

  1. The simplest method is to use lid. The canning lids that come with the jars can and will have a galvanic reaction to the acids from the ferment. Unless you enjoy bits of metal in your kefir, try a plastic lid instead (which is much more inert).

You can do a loose lid or tight lid if you are adventurous. A loose lid is basically just setting the lid on top of the jar without screwing it on. It’s safe because if there is an excessive amount of carbonation it will be able to escape. However, it does not create a seal and is not truly anaerobic. And some people consider that the best of both worlds. But it will still be at-least partially anaerobic and will change the ferment.

A closed tightened lid will create a strong anaerobic environment, however you do risk explosion. Typically it won’t create enough carbonation to break through the jar during the first ferment, but there are rare exceptions. Also there are people who claim that the seal is not strong enough for a true anaerobic environment. For that you need an airlock.

  1. Basic airlockWater-less airlocks are the cheapest and simplest way to get the benefit of an airlock. The air simply vents when needed. It’s not as good as the 3 piece traditional airlock, but it will do the job. We offer these airlocks with a plastic lid bad instead, so you can use that instead of the metal lid bands that come with the jar.


  1. Traditional 3-piece air lock. These are the best and perhaps the only way to get a true anaerobic ferment. If you are looking the the ultimate anaerobic environment, then these air locks are a must have.

Bottom line

Water kefir can be fermented aerobically (with oxygen / open lid) or anaerobically (without oxygen / closed lid). Both have the advantages and disadvantages and it comes down to personal preference.

Water kefir aerobic (open lid) ferments

  • The Acetic Acid Bacteria (the vinegar makers) will thrive
  • Low oxygen bacteria like Bifidobacterium do NOT thrive
  • Greater yeast content
  • Higher risk of contamination

Water kefir anaerobic ferments

  • Less Acetic Acid Bacteria and less vinegar
  • Lower yeast content
  • Lower risk of contamination

So, which method do you prefer?