Mantenerlo en marcha

Most kombucha guides end at the first successful batch. The interesting part is month six.

Is it mould?

• Brown stringy strands hanging from the SCOBY: yeast. Normal, harmless, often a sign of a vigorous culture.
• Bumpy, dry, fuzzy circles sitting on top — white, green, blue or black: mould. Discard everything, including the starter liquid, and begin again from a fresh culture. Do not attempt to scrape it off. This is the one non-negotiable rule.

Mould almost always means too little starter liquid, too cold a room, or a lid that trapped moisture. Acidity is the defence: always start a batch at pH below 4.5.

Too sour

You left F1 too long, or the room is warm. Kombucha does not go back — but a vinegar-sharp batch is excellent for salad dressing, for deglazing, and as starter liquid for the next round. Shorten F1 to 6–8 days in summer.

Flat

Not enough sugar at bottling, a leaking gasket, or too much headspace. Check the gasket first: it is usually the gasket.

Going away

Kombucha is patient. Up to three weeks: leave F1 running; you will get a sour batch, which is useful as starter. Longer: put the SCOBY and 500 ml of mature liquid in a jar in the fridge, covered with cloth. It will be sluggish for a batch or two on return, then fine.

Continuous brew

A tap jar you draw from and top up. It halves handling, produces more consistent acidity, and — because you never fully empty it — makes mould less likely. The cost is a larger vessel and a plastic tap unless you buy a stainless one. Worth it once you are past three months of consistent brewing.

When to stop

If you are pouring batches away, stop. A dormant SCOBY in the fridge costs nothing and waits indefinitely. The point of making your own is not virtue — it is that it is cheaper, better, and produces almost no waste when you are actually drinking it.