Does a Sinking SCOBY Mean My Batch of Kombucha Is Ruined?

If you brew your own kombucha frequently, you’ll notice that the SCOBY isn’t stationary. You will likely see a floating and sinking SCOBY in the same batch. Neither position is cause for concern. Many factors affect a homebrew and kombucha SCOBY positioning.

Is a SCOBY Supposed to Float?

A SCOBY (symbiotic culture of bacteria and yeast) does not have to float to ferment and fill your kombucha with beneficial probiotics. If your starter tea is brewed correctly, you’ll have healthy kombucha with enough acidity to ferment successfully.

Some SCOBYs float on top of your brew, while other SCOBYs sink or even float sideways. As long as your SCOBY isn’t moldy, it should be safe.

Is a Sinking SCOBY Normal?

It’s normal for a SCOBY to sink to the bottom of the jar.

SCOBYs are living cultures, and they grow throughout their lives. While kombucha ferments, a SCOBY produces carbon dioxide. The activity of carbon dioxide is what causes the SCOBY to move around in your homemade kombucha.

You’ll notice two types of SCOBYs when you brew kombucha: the mother SCOBY and the baby SCOBY.

The mother SCOBY is the SCOBY you start your new batch with, and it begins the fermentation process. The mother SCOBY doesn’t grow but can accumulate yeast strings throughout its life. Usually, the mother SCOBY sinks, but if it floats, it’s okay.

The baby SCOBY forms on top of your brew during the first fermentation. The longer you let your new batch ferment, the thicker your new baby SCOBY will get. Leave your brew undisturbed during the first fermentation so the baby SCOBY grows strong. Treat it like your mother SCOBY, leaving it behind as you bottle your new brew for the second fermentation.

Once you have multiple SCOBYs in your homebrew, set some up in a SCOBY hotel before starting your next batch of kombucha.

What Causes a SCOBY to Sink?

SCOBYs sink for three reasons:

1. Bacteria population: SCOBYs are full of good bacteria and yeast, but sometimes one side of a SCOBY has more bacteria than the other side. This imbalance can cause the SCOBY to sink or turn sideways.
2. Density: SCOBYs are denser than kombucha tea. As your SCOBY grows and becomes denser, it’s more likely to sink.
3. Low temperature: the ideal fermentation temperature is between 68 and 78 °F. If your brew is too cool, your SCOBY can turn sluggish and sink. In colder weather, SCOBYs are more likely to sink. Check the temperature of your homebrew with a temperature strip and either move it to a different location or invest in a kombucha heating wrap.

Should You Try to Move the SCOBY?

Ideally, your SCOBY should be submerged under your sweet tea. This allows it to ferment effectively and stops mold from growing. The more a SCOBY is exposed to air, the more risk it will get moldy. Before trying to move your SCOBY, check the temperature of your brew as directed above and make adjustments as needed.

Let your new SCOBY grow for at least seven days undisturbed. If you’d like to push it down afterward, thoroughly wash your hands and gently push your SCOBY into your sweet tea.

How Do You Know if a SCOBY Is Healthy?

Healthy SCOBYs range from white to brown and have strings of yeast hanging off their surface.

You should also be able to handle it gently without it falling apart. To keep your SCOBY as healthy as possible, use pure green or black tea when setting up your first fermentation, and keep all supplies clean and your concoction at room temperature.

4 Signs It’s Time to Replace Your SCOBY

Sometimes living cultures just aren’t successful. If you notice any of these signs on your mother SCOBY, it’s time to replace it with a new SCOBY.

1. Black spots: black spots mean your SCOBY is dying or you already have a dead SCOBY.
2. Gray or green mold: usually, these colors indicate your brewing temperature fluctuated widely. Mold means your brew is unsafe.
3. Sour taste, overly sweet, or no carbonation: your SCOBY is sluggish and not properly fermenting your kombucha tea. If your tea tastes very sweet after the first fermentation, your homebrew may be unsafe to drink. Large temperature drops can weaken your SCOBY and make your brew taste sour. Kombucha gets fizzy during its second fermentation but should be slightly carbonated after the first fermentation.
4. White, feathery mold: SCOBYs exposed to air for long periods grow white mold. Your homebrew is not safe to drink.

SCOBYs last for months when properly cared for. For successful brewing, you need good quality tea, cane sugar, and stable temperatures.