Kombucha Troubleshooting: 22 Common Problems and How to Fix Them
Something has gone wrong with your kombucha. You’re not sure what, and you’re not sure whether to salvage it or start again.
This kombucha troubleshooting guide covers every common problem — taste issues, carbonation problems, SCOBY appearance concerns and signs of genuine contamination. Each section explains what’s happening, whether it’s actually a problem, and exactly what to do about it.
If you’re new to kombucha and want to understand the full brewing process first, start with my complete beginner’s guide. If something specific has gone wrong and you need answers quickly, find your problem in the sections below.
Taste Problems
1. My kombucha tastes too sweet
What’s happening: Fermentation hasn’t completed yet. The SCOBY hasn’t had enough time or warmth to convert the sugar into acids.
Is it a problem: No — it just needs more time.
What to do: Leave it for another 2–3 days and taste again. If your kitchen is below 20°C, move the jar somewhere warmer — temperature is the biggest factor in fermentation speed. Check my post on how long kombucha takes to ferment for typical timelines at different temperatures.
2. My kombucha tastes like vinegar
What’s happening: Over-fermentation. The bacteria have converted most of the available sugar into acetic acid, pushing the flavour past tangy into sharp and vinegary.
Is it a problem: Not a safety problem — over-fermented kombucha is completely safe. It’s a flavour problem.
What to do: Use this batch as starter liquid for your next brew — it’s excellent for that purpose and highly acidic which protects new batches well. In cooking, it works like apple cider vinegar in dressings, marinades and deglazing. Next batch, reduce fermentation time by 2–3 days and taste from day 7 rather than waiting. Full details in my post on why kombucha tastes like vinegar.
3. My kombucha tastes flat and bland
What’s happening: Either the tea was too weak, the fermentation temperature was too low, or the batch was harvested too early.
Is it a problem: Not a safety problem — just a flavour one.
What to do: Leave it another 2–3 days if it still smells right. For future batches, try stronger tea (3–4 bags per litre rather than 2), ensure the brewing temperature is consistently above 21°C and taste from day 7 to catch it at the right moment.
4. My kombucha tastes metallic
What’s happening: Metal contact during brewing or fermentation. Metal reacts with acidic kombucha, leaching compounds into the liquid.
Is it a problem: Yes — discard this batch.
What to do: Check your equipment. Brief contact with stainless steel during brewing (stirring, pouring through a strainer) is fine. Prolonged contact — fermenting or storing in a metal container, leaving a metal spoon in the jar — is not. Switch to glass, plastic or wood for anything that touches the kombucha for more than a few seconds.
5. My kombucha tastes soapy or perfumed
What’s happening: Almost certainly lavender or another floral flavouring added in too large a quantity during second fermentation. Lavender especially intensifies significantly during fermentation.
Is it a problem: Not a safety problem — just unpleasant.
What to do: This batch is probably not salvageable as a drink but can be used in cooking. Next batch, use significantly less lavender — half a teaspoon of dried culinary lavender per 500ml is the maximum, and starting with a quarter teaspoon and increasing is safer.
6. My kombucha has a strange aftertaste
What’s happening: Usually one of three things — residual soap on equipment, flavoured/herbal/oily tea used in the first ferment, or a stressed SCOBY producing off-compounds (often from a low tannin/caffeine tea like white tea or a weak/young culture).
Is it a problem: Depends on the source, but all three are fixable.
What to do: Rinse all equipment thoroughly with hot water only — no soap residue should remain, and a vinegar rinse before use helps if you’re unsure. Use plain, unflavoured true tea (black, green, white or oolong) for first fermentation, and avoid anything with oils or added flavouring — even trace amounts can throw off the taste. If neither of those is the cause, consider your tea strength: a weak or low-tannin tea (like white tea) can leave a stressed SCOBY producing unusual flavours — switch to black or green tea for a few batches to let the culture recover. If the taste persists across multiple batches after ruling those out, check your water — heavily chlorinated tap water is a common culprit; switch to filtered or dechlorinated water.
Carbonation Problems
7. My kombucha has no fizz after second fermentation
What’s happening: One of seven possible causes — leaking gasket, room too cold, not enough sugar, over-fermented first batch, refrigerated before bottling, not enough time, or too much headspace.
Is it a problem: Not a safety problem — just a disappointing result.
What to do: Work through each possible cause systematically. My full guide on why kombucha has no fizz covers every cause and fix in detail. Once you’ve got good carbonation, open it carefully — see #8 for safe opening technique to avoid a mess (or worse) on your first sip.
8. My kombucha is too fizzy and explodes when opened
What’s happening: Over-carbonation from second fermentation running too long or at too high a temperature.
Is it a problem: Potentially — over-pressurised bottles can be dangerous if opened incorrectly.
What to do: Always open cold, slowly, over the sink. If you suspect a bottle is over-pressurised, refrigerate it for several hours before opening. For future batches, refrigerate sooner — once the bottle hisses when cracked open, it’s ready. Don’t leave bottles at room temperature hoping for more fizz once they’re already well carbonated.
9. My kombucha loses fizz quickly after opening
What’s happening: Either the carbonation was borderline to begin with, the bottle was opened warm, or it was poured too aggressively.
Is it a problem: No — just disappointing.
What to do: Open and serve cold. Pour slowly down the side of the glass rather than straight down the centre. Drink soon after opening — kombucha doesn’t hold its fizz for long once the bottle is open, unlike commercial carbonated drinks which have CO2 injected under much higher pressure. If you’re also finding bottles more pressurised than expected when you crack them, check #8 for how to open safely.
SCOBY Appearance Problems
10. My SCOBY is brown
What’s happening: Tea tannins staining the SCOBY over successive batches. Completely normal and expected.
Is it a problem: No.
What to do: Nothing. A brown SCOBY is a healthy, well-used SCOBY. The colour will continue to deepen over time.
11. My SCOBY has holes in it
What’s happening: Normal structural variation in SCOBY growth. SCOBYs don’t need to be solid discs to function effectively.
Is it a problem: No.
What to do: Nothing.
12. My SCOBY sank to the bottom
What’s happening: Normal. SCOBYs don’t need to float to work. A new SCOBY layer will form on the surface of the liquid within a few days regardless of where the original one settles.
Is it a problem: No.
What to do: Nothing. Leave it and allow the new surface layer to form.
13. My SCOBY is very thin
What’s happening: Either the fermentation temperature is too low, the batch didn’t run long enough to grow a substantial new layer, or the culture is weakened — sometimes from a low-tannin tea like white tea, which doesn’t give the SCOBY enough to work with.
Is it a problem: Worth monitoring.
What to do: Move to a warmer location and allow more time. A thin SCOBY will thicken over successive batches as conditions improve. If it remains very thin after 3–4 batches in good conditions, the culture may be weakened — try using more starter liquid (200–300ml per litre) to give it stronger protection.
Tea choice matters here too. This isn’t something that’s been formally studied, but it’s a consistent observation across experienced brewers and kombucha educators: black tea’s higher tannin and caffeine content tends to correlate with faster, thicker SCOBY growth, likely because it simply gives the culture more to feed on. Green tea is a decent second choice and won’t harm the culture, but white tea and other low-tannin teas are the ones most often linked to thin, slow-growing SCOBYs — better saved for once your culture is already robust.
14. My SCOBY is enormous and very thick
What’s happening: Healthy, active fermentation over many batches. Each batch grows a new layer which fuses to the existing disc.
Is it a problem: No — but it can become unwieldy.
What to do: Peel the oldest, darkest layers from the bottom and compost them. Keep the top 2–3 layers in your brewing jar and put the rest in your SCOBY hotel.
15. My SCOBY has brown stringy bits underneath
What’s happening: Yeast strands — completely normal and a sign of active fermentation. The yeast in the SCOBY collects underneath and hangs into the liquid.
Is it a problem: No.
What to do: Nothing during fermentation. Strain them out when bottling if you prefer a cleaner result.
16. My SCOBY has fuzzy growth on the top surface
What’s happening: Mould. The only genuinely serious SCOBY problem. Fuzzy growth — raised, fluffy, green, black, pink or white — on the exposed top surface is mould, not yeast activity.
Is it a problem: Yes — discard the entire batch immediately!
What to do: Do not try to remove the mould and continue. Discard the kombucha and the SCOBY. Sterilise the jar thoroughly with hot water and white vinegar. Start again with a fresh SCOBY and generous starter liquid — at least 200ml per litre — which acidifies the new batch immediately and creates conditions hostile to contamination. For full details on distinguishing mould from normal SCOBY appearance, read my healthy SCOBY guide.
17. My SCOBY smells wrong
What’s happening: Normal kombucha smells sharp and tangy — like apple cider vinegar but milder and slightly sweet. A smell like genuine rot, something foul or obviously wrong, is a warning sign.
Is it a problem: Trust your instincts. If the smell makes you recoil rather than just wrinkle your nose at the sharpness, something is wrong.
What to do: Check the SCOBY surface carefully for mould. If you find fuzzy growth, discard and start again. If you find no visible mould but the smell persists across 2–3 days, it’s worth discarding and starting fresh — a genuinely off smell is not something to push through.
Process Problems
18. No new SCOBY is forming
What’s happening: Usually temperature — below 18°C fermentation slows so dramatically that new SCOBY growth stalls. Also possible if the starter liquid was insufficient or the culture was weakened.
Is it a problem: Worth fixing.
What to do: Move to a warmer location above 21°C. Check you used at least 100–200ml of starter liquid. If the temperature and starter liquid are correct and still no new SCOBY forms after 10 days, the culture may be weakened — use more starter liquid next batch and consider sourcing a fresh SCOBY from your hotel if you have one. Read my SCOBY hotel guide for how to store them properly.
19. My kombucha is very cloudy
What’s happening: Active yeast in the liquid — completely normal. Commercial kombucha is often filtered and pasteurised, which removes the cloudiness. Home-brewed kombucha is alive and unfiltered.
Is it a problem: No.
What to do: Nothing. Strain when pouring if you prefer a clearer result. The cloudiness is harmless and means the culture is active.
20. My kombucha has white bits floating in it
What’s happening: Yeast clumps — the same yeast that forms strands under the SCOBY sometimes detaches and floats through the liquid. Completely harmless.
Is it a problem: No.
What to do: Strain when pouring if you prefer a cleaner result.
21. Fermentation seems very slow
What’s happening: Almost always temperature. Below 20°C, fermentation can take twice as long as at 24°C. A weakened culture can also slow fermentation.
Is it a problem: Not immediately — but worth addressing.
What to do: Find a warmer spot for your brewing jar. Check the temperature with a thermometer. Above 21°C is the target. If the temperature is right and fermentation is still slow, check your starter liquid quantity — too little starter means the early fermentation is poorly protected and the culture has to work harder to establish itself. Read my post on how long kombucha takes to ferment for typical timelines.
22. My SCOBY hotel smells very vinegary
What’s happening: Normal. The liquid in a SCOBY hotel is highly acidic finished kombucha, which smells sharp. This is correct and means the hotel is maintaining its acidity — which is what protects the SCOBYs.
Is it a problem: No.
What to do: Nothing — unless the smell crosses from sharp vinegar into something genuinely foul, in which case check for mould and consider discarding if anything looks wrong.
Quick Reference — Is This Normal?
| What you’re seeing | Normal? | Action needed |
|---|---|---|
| Brown SCOBY | ✅ Yes | None |
| Holes in SCOBY | ✅ Yes | None |
| SCOBY sank | ✅ Yes | None |
| Yeast strands underneath | ✅ Yes | Strain when bottling if preferred |
| White floating bits | ✅ Yes | Strain when bottling if preferred |
| Cloudy liquid | ✅ Yes | None |
| New thin layer on surface | ✅ Yes | None |
| Brown patches on SCOBY | ✅ Yes | None |
| Very thick SCOBY | ✅ Yes | Peel old layers |
| Kombucha too sweet | ⚠️ Not yet ready | Wait 2–3 more days |
| Kombucha too sour | ⚠️ Over-fermented | Use as starter liquid |
| No fizz after bottling | ⚠️ Fix needed | Check gaskets, temperature, sugar |
| Very thin SCOBY | ⚠️ Monitor | Warmer location, more starter liquid |
| Fuzzy mould on SCOBY | ❌ Serious | Discard entire batch |
| Metallic taste | ❌ Serious | Discard, check equipment |
| Foul rotten smell | ❌ Serious | Discard, check for mould |
When to Discard and Start Again
Most kombucha problems are fixable or cosmetic. The situations where discarding is the right call:
- Fuzzy mould of any colour on the top surface of the SCOBY
- Metallic taste indicating metal contamination
- Genuinely foul smell — not sharp vinegar, but something that smells rotten or obviously wrong
- Persistent off-taste across multiple batches that doesn’t improve with corrected conditions
Everything else — the brown, the holes, the strands, the cloudiness, the sourness — is either normal or fixable without starting from scratch.
Still stuck? Drop a comment on any post with the details of your batch, and I’ll help you figure out what’s going on. I’ve seen most of what kombucha can do.
New to kombucha? Start with my complete beginner’s guide to brewing kombucha at home.
Sources
Jayabalan, R., Malbaša, R. V., Lončar, E. S., Vitas, J. S., & Sathishkumar, M. (2014). A review on kombucha tea — microbiology, composition, fermentation, beneficial effects, toxicity, and tea fungus. Comprehensive Reviews in Food Science and Food Safety, 13(4), 538–550. https://doi.org/10.1111/1541-4337.12073
Crum, H., & LaGory, A. (2016). The big book of kombucha. Storey Publishing.
