Kombucha FAQ’s
Kombucha FAQ: Every Brewing and Troubleshooting Question Answered
The Short Answer
Most kombucha problems come down to four things: starter liquid acidity, tea and sugar quality, temperature and airflow. This page answers every common question about brewing, SCOBY health, ratios, carbonation and storage. New to kombucha? Start with our how to make kombucha guide first, then come back here when specific questions come up.
We have been helping home brewers across Ireland master the art of making kombucha since 2019 and these are the questions that come up most often. From SCOBY health and starter liquid ratios to getting the second fermentation fizz right every time, everything you need is here in one place.
Starting your first kombucha batch raises a lot of questions. Is that brown stringy bit normal? Why did my SCOBY sink? Why is there no fizz? The answers almost always come back to the same four fundamentals. Get these right and most problems disappear before they start.
The 4 Fundamentals of Successful Kombucha Brewing
1. Tea and Sugar: The SCOBY’s Only Food Source
A sluggish or weak SCOBY is almost always a nutrition problem. Kombucha requires the nitrogen, tannins and caffeine found in real tea from the Camellia sinensis plant, which means black or green tea. Herbal teas, fruit teas and flavoured blends like Earl Grey contain essential oils and additives that can actively weaken or stress the culture over time. Stick to plain organic black or green tea for every batch.
The sugar in kombucha is not for you, it is the fuel the SCOBY consumes during fermentation. Organic cane sugar is the cleanest option as it contains no residual chemicals that could interfere with the culture. The SCOBY converts the sugar into organic acids, B vitamins and carbon dioxide over the course of the fermentation cycle.
2. Starter Liquid: Your First Line of Defence Against Mould
Starter liquid is finished kombucha from a previous batch and it is not optional. Its job is to immediately lower the pH of your fresh sweet tea to below 4.5 before fermentation begins, creating an acidic environment where beneficial bacteria thrive and mould cannot take hold. Without sufficient starter liquid your brew is vulnerable in the first 24 to 48 hours when the culture has not yet had time to acidify the liquid naturally.
✎ Target pH ranges: your brew should start at pH 4.5 or lower and finish between 2.5 and 3.5. pH test strips are the easiest way to monitor this, particularly for your first few batches.
3. Airflow: Why Kombucha Needs to Breathe
Kombucha is an aerobic ferment, meaning the SCOBY needs access to oxygen to function correctly. The bacteria use oxygen to convert ethanol into acetic acid, which is one of the key organic acids responsible for kombucha’s flavour and preservation properties. Cover your jar with a tightly woven muslin cloth or coffee filter secured with a rubber band. This allows constant airflow while keeping out fruit flies, dust and contaminants. Never seal your jar with an airtight lid during first fermentation as this will stall the process and stress the culture.
4. The Self Replicating SCOBY: Why You Will Never Run Out
Every batch of kombucha you brew produces a new layer of SCOBY on the surface of the liquid. This new layer, sometimes called a baby SCOBY, is a natural byproduct of the fermentation process and a sign that your culture is healthy and active. Over time you will accumulate more SCOBY than you need, which can be shared with friends, composted or stored in a SCOBY hotel as a backup culture. A NutriBrew SCOBY cared for properly will continue producing indefinitely, batch after batch.
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Shop Fresh Kombucha SCOBYs →SCOBY Health & Troubleshooting
No, a sinking SCOBY is completely normal and not a sign that anything is wrong with the culture. SCOBYs can float, sink or hang at any angle depending on their density, the temperature of the liquid and how carbonated the brew is. What matters is what forms on the surface, not where the original SCOBY sits. A new translucent layer will begin to form at the top of the liquid regardless of where the original culture ends up.
These are yeast strands and they are a sign of a healthy, active fermentation. During brewing, yeast cells clump together into visible strands or clusters that float through the liquid or settle at the bottom. They are completely harmless and have no effect on flavour or safety. If you prefer a cleaner pour, simply strain your kombucha through a fine mesh strainer before drinking or bottling.
New SCOBY growth is driven primarily by temperature and surface area. In a cool Irish kitchen below 20°C, it can take 10 to 14 days before a visible new layer appears. Make sure your brewing jar has a wide mouth to give the culture as much surface area as possible, and move it to a warmer spot if the kitchen is cool. A thin translucent film forming on the surface, even a barely visible one, is your new SCOBY beginning to grow.
Fuzzy dry growth in green, white or black is mould and the entire batch should be discarded immediately, including the SCOBY and all the liquid. Do not try to salvage it. Mould is rare and usually caused by insufficient starter liquid at the start of the batch, a very cold brewing environment or a contaminated jar. Sterilise your vessel thoroughly with white vinegar, start fresh with a new SCOBY and make sure your starter liquid is added before fermentation begins.
This is a common issue in cooler kitchens and points to a yeast imbalance. The bacteria in the SCOBY are producing acetic acid, which creates the vinegar smell, but the yeast responsible for producing CO2 is moving too slowly in the cold to generate enough gas for carbonation. Stir your starter liquid before adding it to the next batch to distribute the yeast evenly, and aim to keep your brewing temperature between 20 and 24°C consistently. The yeast needs warmth to do its job.
Holes in a SCOBY are caused by CO2 bubbles produced by the yeast pushing upward through the culture as they try to escape. If the SCOBY is thin or still developing, the gas creates small tears as it passes through. This is a sign of active fermentation, not damage. As your brew matures and the SCOBY builds up additional layers with each batch, the holes typically fill in and become less noticeable.
Yes, completely safe. The sediment is dormant yeast that has settled out of the liquid as fermentation slowed down. It is a natural byproduct of a living drink and is not harmful in any way. You can swirl the bottle gently before opening to incorporate it back into the liquid, or leave the last few millilitres in the bottle if you prefer a cleaner pour.
A syrupy or rope-like texture is usually caused by an overgrowth of a specific strain of bacteria, often triggered by using too much sugar or brewing at temperatures above 26°C. It is not harmful but the texture is unpleasant to drink. To fix it, use slightly less sugar in your next batch, clean your brewing vessel thoroughly with white vinegar before starting again, and keep the temperature closer to 22 to 23°C.
Precision Ratios & Ingredients
Plain black or green tea from the Camellia sinensis plant is the best choice for kombucha. These teas contain the tannins, nitrogen and caffeine that the SCOBY needs to stay healthy and productive. Organic loose leaf or bagged black tea is the most reliable option for beginners. Avoid flavoured teas, herbal blends and anything containing essential oils such as Earl Grey, as these compounds can stress or weaken the culture over time.
Organic cane sugar is the most reliable option. It dissolves cleanly, contains no residual chemicals that could affect the culture, and provides a straightforward food source for the yeast and bacteria to convert into organic acids. Avoid honey, coconut sugar, stevia or artificial sweeteners. These either ferment unpredictably or cannot be used by the SCOBY at all.
pH test strips remove the guesswork from two critical safety checks. At the start of fermentation your sweetened tea should have a pH of 4.5 or lower after adding your starter liquid. This acidic environment prevents mould from taking hold in the early stages. At the end of fermentation your finished kombucha should sit between pH 2.5 and 3.5. Strips are inexpensive and give you a clear indication of whether your brew is developing as it should.
Yes. Every SCOBY develops its own unique microbial profile based on the tea it was originally cultured in and the environment it has been maintained in. NutriBrew SCOBYs are heirloom cultures that have been grown and maintained over many batches rather than produced in a single commercial cycle. They are lab tested for microbial diversity and designed to be self sustaining indefinitely with proper care.
Irish tap water contains chlorine and sometimes chloramines, which are added to make it safe to drink but can weaken a live culture over time. Filtered or still mineral water is the better choice. If you only have access to tap water, boil it for 10 to 15 minutes and allow it to cool completely before using, or leave it in an open container overnight to allow the chlorine to evaporate naturally.
The Fermentation Cycle
Taste is the only reliable way to judge readiness. From day 7 onwards, dip a clean straw below the SCOBY, cover the top with your finger to trap a small amount and taste it. If it is still quite sweet, leave it for another 2 to 3 days and taste again. If it has a pleasant balance of tangy and lightly sweet, it is ready. If it tastes strongly of vinegar, harvest immediately and use it as potent starter liquid for your next batch rather than drinking it on its own.
The ideal range is 20 to 26°C. Within this range the bacteria and yeast in the SCOBY work at a balanced pace, producing a well rounded flavour without the brew becoming overly sour too quickly. Below 20°C fermentation slows significantly and the risk of mould increases as the culture takes longer to acidify the liquid. Above 26°C the brew moves too fast and can become very sour within a few days. In an Irish winter, a warm cupboard, an airing press or the top of a fridge are all reliable spots for maintaining a consistent temperature.
Yes, in most cases. A new layer of SCOBY, sometimes called a baby SCOBY, forms on the surface of the liquid during each fermentation cycle as the bacteria produce cellulose. The thickness and speed of growth depends on temperature, the sugar content of the brew and the surface area of your jar. A wide mouthed jar at a consistent 22 to 24°C will produce the most reliable new growth. Over time you will have more SCOBY than you need, which can be shared, composted or stored in a SCOBY hotel.
Use swing top bottles designed to handle pressure and burp them once daily by opening briefly over a sink to release excess gas. Once you hear a healthy hiss when you open a bottle, move all bottles to the fridge immediately. Cold temperatures stop the yeast from producing more CO2 and lock the carbonation in at the level you want. Never leave sealed bottles unattended at room temperature for more than 3 days, particularly in summer or in a kitchen above 22°C.
Maintenance & Storage
Yes, a well maintained SCOBY can be used indefinitely. When you want to take a break from brewing, create what is sometimes called a SCOBY hotel. Place your SCOBY in a clean jar with enough fresh sweet tea to keep it submerged and leave it at room temperature rather than in the fridge. It will continue fermenting slowly and become very acidic over time, which actually makes it an excellent source of potent starter liquid when you return. Check it every 2 to 3 weeks and add a small amount of fresh sweet tea if the liquid level drops significantly.
Properly bottled kombucha stored in the fridge will keep well for 3 to 4 weeks. The cold temperature slows fermentation to a near stop, preserving the flavour profile and preventing the brew from continuing to sour. The flavour does continue to develop slowly even in the fridge, so a bottle opened after two weeks will often taste noticeably more complex than one opened on day one. Always open bottles slowly over a sink after any extended fridge storage.
No, the fridge is not a good long term storage option for a SCOBY. Cold temperatures put the bacteria into a deep dormancy while the yeast remains partially active, which creates an imbalance in the culture that can make it difficult to revive and more susceptible to mould when brought back to room temperature. For breaks of up to 6 weeks, keep the SCOBY in a jar of sweet tea at room temperature. It will be fine and ready to brew again whenever you are.
A SCOBY hotel is simply a jar where you store spare SCOBY layers that accumulate over time as your culture grows with each batch. It serves two purposes. First, it acts as a backup in case a batch develops mould and you need to start fresh without waiting for a new SCOBY to arrive. Second, the liquid in a SCOBY hotel becomes extremely acidic over time, making it one of the most effective starter liquids available for protecting new batches. You do not need one immediately but it becomes useful once you have been brewing for a few months and have accumulated extra cultures.
Your Kombucha Will Keep Getting Better
Every SCOBY takes a few batches to fully settle into its new environment. Your water, your kitchen temperature and the tea you use all influence how the culture develops, and it is completely normal for the first batch or two to taste different from what you expected. By the third or fourth batch most brewers notice a marked improvement in flavour, carbonation and consistency as the culture acclimatises and finds its rhythm.
Once you are comfortable with the basics, the real enjoyment of kombucha brewing begins. Small changes to your tea blend, fermentation time or second fermentation ingredients produce noticeably different results. There is no single correct kombucha. Over time you will develop a process that suits your taste, your kitchen and your routine, and the drink you produce will be entirely your own.
If you run into any issues along the way, every question has an answer somewhere in this guide. And if you cannot find what you are looking for, our team are always happy to help. We have been brewing and supporting home fermenters across Ireland since 2019 and we have seen just about everything.