Why Does My SCOBY Sink? Causes and What to Do

A sinking SCOBY is usually normal and rarely means the batch has failed. Leave the jar alone, and a new layer will usually form at the surface. Judge the brew by its smell and taste, not by where the SCOBY is sitting.

Why SCOBYs sink

Gas trapped under the mat. Yeasts produce carbon dioxide, and bubbles trapped under or in the SCOBY help it float. Slower activity means fewer bubbles, so the mat can sink.
Cool temperatures. Cooler rooms slow the yeast and bacteria, so less gas is made.
Movement. Moving, tilting or swirling the jar can knock bubbles loose. Tasting the brew can do the same.
A young culture. A young SCOBY may not yet produce enough gas to keep the mat on top.

What’s normal

Sinking to the bottom, floating halfway, or sitting at an angle
A thin, cloudy-white film forming on the surface
Brown strands hanging below the mat

Sinking, rising and sitting sideways are all normal, and none of them affects fermentation.

What to do

Leave it alone. Don’t move the jar. A new film will usually form at the top.
Check the temperature. Aim for a warm spot, around 22–27°C (72–80°F). If your room runs cool, see do you need a heating pad for kombucha?
Taste gently. Use a clean spoon or straw, and don’t swirl the jar. Look for the brew becoming less sweet and more tart.
Look for mold, not position. Only worry about fuzzy growth or a rotten smell. Is it mold or a healthy SCOBY? explains how to tell.
Give it time. A young culture may need more time to settle.

Signs your batch is working

The liquid is less sweet over time
Small bubbles or fizz
A new film forming or thickening
A fresh, sour smell

You don’t need all of these. It is normal for only one to show at first.

When to worry

Fuzzy mold in any colour: discard the batch.
A rotten smell: discard the batch.
No change after about two weeks. If the liquid stays sweet and nothing seems to be happening, the culture may not be active. Some guides use about 15 days as a rule of thumb. If so, start again with a fresh SCOBY and fresh starter, using the step-by-step guide.