How to Fix a Stuck Ferment: A Simple 4-Step Guide

Few things are more frustrating than watching your ferment bubble away, only for it to suddenly stop while your hydrometer still shows sugar in the wash.

That is what we call a stuck ferment (also known as a stalled ferment).

The good news is that most stuck ferments can be fixed with a bit of troubleshooting. Here is a simple four-step guide to get things moving again.

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Step 1: Check if It Is Really Stuck

First grab your triple scale hydrometer. Many people think their ferment has stalled when in fact it has already finished.

If your SG reading is 1.000 or lower, the ferment is complete.
If the reading is higher, then it is time to move on to the next checks.

Step 2: Check the Temperature

Temperature is the most common cause of a stuck ferment. Yeast needs the right conditions to stay active.

Keep the wash at the upper end of the yeast’s recommended range.
A fish tank or aquarium heater can help maintain a steady temperature.
If the wash is too cold, the yeast slows down or stops.
If the wash is too hot, the yeast can die.

If the yeast is already stressed or inactive, you may need to repitch with fresh yeast.

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Step 3: Check the pH

Yeast does not like extremes of pH. Too low or too high and they will not work properly.

The best pH for fermentation is around 5.2.
Yeast struggles below 4.0 and above 6.0.

Adjustments are easy:

Use lemon juice or citric acid to lower the pH.
Use baking soda or potassium bicarbonate to raise the pH.

If the yeast is badly affected, repitching with fresh yeast may be needed.

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Step 4: Check Nutrient Levels

If temperature and pH are both fine, then the problem may be a lack of nutrients. This is very common in high-gravity sugar washes, which do not provide yeast with all the minerals and vitamins they need.

The fix is simple:

Add a proper yeast nutrient blend.
Follow the manufacturer’s instructions for dosage.

This will usually get the ferment going again.

When All Else Fails

If you have checked all four steps and the ferment still will not restart, then your hydrometer is probably reading unfermentable sugars or unconverted starches.

If that is the case, the ferment is not stuck at all, it is simply finished. Time to distil.

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Final Tip

A stuck ferment is usually nothing to panic about. In most cases it comes down to temperature, pH, or nutrients. Work through the steps one by one and you will soon have your yeast back on track.

Until next time… Happy Distilling!

Cheers