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Kombucha Brewing/SCOBY FAQ

What is a SCOBY?

*SCOBY stands for Symbiotic Colony Of Bacteria and Yeast. The Kombucha SCOBY is a cooperative of microorganisms that feed on tea and sugar and whose products of metabolism make up the delicious and healthful beverage.

*A SCOBY is sometimes also called a mother, starter, mushroom or kombucha culture. It very often is looked at as an intelligent life-form that has feelings. Rest assured, although an amazing microbial colony, it is no different than any other microbe in the fermentation world. Don’t anthropomorphize your SCOBY!

When we use the word SCOBY in the following text we are referring to the entire microbial colony of bacteria and yeast in the cellulose patty (culture) as well as the starter liquid.


The three main rules for a lifetime of perfect kombucha are:

  • Fresh healthy SCOBY and starter liquid every brew. Start with the best SCOBY and starter you can get your hands on (the SCOBYs that come from our lab are the best of the best).  When you are starting your next batch, use ONLY the newest SCOBY that has formed on the surface and liquid starter from the top of the vessel. If you are pouring, that’s the first cup (or cups, if you are brewing more than one gallon at a time) of kombucha, not the last. By doing these two things you are keeping your microbial colony diverse and in balance. If you are keeping old SCOBY in your brew, Acetobacter (most dominant bacteria in the SCOBY and the one responsible for making acetic acid which is the acid that tastes like strong vinegar) takes over and you will make tea vinegar, not a delicious and diverse beverage. If you use yeasty starter (the liquid at the bottom of the vessel) you will overpopulate the yeast colony and get an unpleasantly boozy brew. This is why we strongly discourage the “continuous brew” method. You are sure to end up with vinegar if you brew that way. See more about the reasons why you should never continuously brew here. If you are looking to take a break from brewing, store your SCOBY in a tightly sealed container IN THE FRIDGE along with enough fresh starter liquid to start another brew. A SCOBY can remain virtually unchanged in the fridge for up to 3 months.
  • Use whole pure ingredients (nutrients) for fermentation. That’s straight tea (white, green, black, oolong, pu-erh, matcha) and processed cane sugar ONLY. Herbs and non-camellia sinensis teas carry great flavors and health benefits, but they do not contain nutrients the SCOBY requires. If you use them, they will not feed the microbes in the SCOBY and depending on the variety, it may actually decimate non-dominant species. Pure tea is what the SCOBY feeds on. If you want to ferment herbs, use a disposable SCOBY from your hotel, not your main mother SCOBY.   Processed cane sugar is the best sugar to use for fermentation. “Raw” or untreated sugars are dense in minerals that, although good for us, gets in the way of the SCOBY trying to feed on sugars (fructose, glucose, and sucrose). If the SCOBY can’t get to the sugar it will have the same effect as above and weaken the colony. Organic is always better for the SCOBY (and you and the planet…), but not necessary.
  • Keep your temperature as steady as possible and within the range. The temperature range for brewing is 68-86F (20-30C), ideally 78-82F (25-27C). The closer you can come to that sweet spot, the better your brew will be. If your temperature is below 68F, your brew will not be actively fermenting and can let unwanted microbes like wild yeast or mold get a foothold. If a steady temperature is a problem in your home, grab a heat mat to heat year round.
Do these three things and you’ll be brewing like a Kombrewmaster.

Troubleshooting and Brewing Problems

Of the ferments that one can make at home, kombucha is one of the easiest to keep safe and healthy. Much of the health of your brew is predetermined by the liquid 'buch starter. When added to the sweetened tea in the proper amount, liquid 'buch starter will immediately lower the pH. This gives your fledgling batch of 'buch an instant competitive advantage over unwanted microbial contaminants like mold.

When a problem does arise, however, it is good to know what you are looking at. The most common foreign invaders are mold, wild yeast, and fruit flies. If any of these happen, toss your entire brew, SCOBY and all, and start over from scratch. These guys will weaken and eventually destroy your brew, not to mention that they may change the flavor and just flat-out make you not want to drink the stuff.

Want to know what active kombucha fermentation looks like everyday of the brew?
Yeast Vs. Mold: ls this mold?
Yeast Strands and blobs: Along with the new SCOBY, you may start to see brown strands forming in the brew. They might hang from the SCOBY or float freely in the brew. These strands are yeast colonies that like to stick together in long chains. Don't fret; they aren't some weird unwanted party crashers. They are part of the brew and will do no harm. If you want to minimize these strands in future brews, filter them out of your liquid 'buch starter before you inoculate your next brew using a mesh strainer. This will limit their growth. Sometimes the yeast will also attach itself to the top of the SCOBY, form blobs, and even dry on the surface, giving the culture dark brown spots or areas that many new brewers easily confuse with mold.

Mold: The most common contamination is mold. Molds are resilient microscopic fungi that can grow on almost any type of nutrient-dense material. We've all let a loaf of bread go a little too long and had greenish, bluish, whitish, fuzzy, soft mold grow on it. The same mold can grow in your kombucha and will do so on the SURFACE of your brew. Never below the surface in the liquid.

Just like bread, when your 'buch gets infiltrated and overtaken by mold, you will know it. A patch of either green, blue, white, or black fuzzy stuff will be growing on top of your new SCOBY, above the surface of the liquid. Many first time brewers will mistake a yeast swell or new SCOBY formation as mold. The way to overcome these freshmen blues is to look at it like a taxonomist. Mold always needs air, so it will always form on the surface of the liquid. It will never form underneath the surface of the liquid. It will either be dry and fuzzy on the surface or look like a separate distinct entity growing in splotches that don't really meld together. Compare yours with the images and pay special attention to the points just mentioned.

If you confirm that you do have mold, don't futz around. Toss the entire batch and start again. It is very hard to remove all mold spores from a liquid ferment. Also, if you have other brews next to a mold swarm, it can easily spread through airborne mold spores, so go ahead and toss those too.

Top 3 reasons for mold:
  • Starter SCOBY and liquid was not a strong colony. This is very common for brewers trying to start their own SCOBY from a commercial bottle of kombucha.
  • The brew temperature was to low. The temperature range for fermenting kombucha is between 68F (20C) – 86F (30C).  If your brew is below that level it will not be active enough to protect from mold. Grab a heat mat if you are having issues here.
  • Improper ingredients (nutrients) were used to make the batch.  If you are using anything outside straight tea and cane sugar you run the risk of mold. We see lots of mold when brewers try to avoid cane sugar or use raw unprocessed sugar. Always use the best purest nutrients to make your kombucha.

Helpful hints to beat mold:

  • Always verify that your sweetened tea is below 90F before adding the SCOBY and liquid 'buch starter.
  • Always keep your fermentation temperature in the right range.
  • Always add the correct amount of starter to your brew.
  • Avoid letting any particulate from your tea into the fermentation vessel.

Related blog entries:
Kombucha and Mold: What You Need to Know
Fruit flies
Fruit Flies (Drosophila melanogaster). These little devils come out of nowhere. Sometimes it feels like they appear out of thin air. They are little warriors that somehow find their way into your brew with even the most careful precautions. Fruit flies like to make a nice home for themselves and their burgeoning families on your SCOBY.

Once there, they will immediately get frisky and start multiplying, making little baby flies, aka larvae, that will creep and crawl all over the surface of your brew. Those little baby devils will eventually hatch and become flies themselves, trapped under your fermentation vessel cover. If left unattended, one fruit fly will create an empire of brothers and sisters claiming your home brew as their own.

If you get an infestation of fruit flies, toss the entire batch and start again. You may be a 'buch brigadier, but dude, you are no match for an army of fruit flies.
Fruit fly traps are easy to make, and might just be the difference between tasty brew or no brew. An empty small-mouth bottle with a paper funnel stuck in it and a splash of kombucha at the bottom will attract flies into entrapment and imminent doom. In the summer months, we catch thousands that way.

Related blog entry:

Fruit Flies & Kombucha

Wild Yeast

Yeast is everywhere, all the time. Having wild yeast fall into your open-air brew is guaranteed. What is not guaranteed is having that wild yeast survive. In an active kombucha brew, wild yeast can’t survive. In a non-active or less active brew, wild yeast can easily take over and destroy your brew leaving unpleasant flavors, aromas, or unpleasantly high alcohol levels.  

Kahm yeast: Is a byproduct of lacto fermentation and can cause funky flavors and smells to form in your brew. It looks like a white threaded layer that forms on the surface. Often confused as a new SCOBY forming, kahm yeast is unmistakable due to its ornate pattern. It is not harmful but because it causes flavor changes should be a reason for starting your brew over.

Wild Saccharomyces yeast: Often something that a brewer of beer or wine is looking to grab, in kombucha this yeast can make an unpleasantly boozy brew. Out of all the wild yeast that can take over, this is the hardest to detect but if you feel like there is more alcohol than acid flavor you can bet on Wild Saccharomyces. This yeast can be overthrown, but it will take time and a strong colony.

If you are unable to diagnose your brew from the FAQ you can email us and we will try to help you out. In order for us to help quickly, please send the following to with the main concern of your brew in the subject line.


1. Aerial shot of entire brew surface showing SCOBY growth, if any.

2. Close up of surface highlighting any area of concern or general SCOBY growth.


3. Profile shot of entire brew

Answer these 5 questions:

  1. What is the average temperature of the brew while it is fermenting?
  2. How long has it been fermenting?
  3. Where did the original SCOBY (mother, mushroom, culture) come from?
  4. How much starter liquid was used?
  5. What tea/blend and sweetener was used, and what quantity?

Average turn around for a “brew tech” email is 3 days. The more information you can give us in the original email the faster we can help.

Brew help disclaimer: This FAQ and all brew tech responses are our opinions only. We are not responsible for anything that could arise from advice given. You as the brewer take all responsibility for your body and your brew. 



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