Finely chop the ginger and turmeric. Quarter the lemon.
Add the turmeric, ginger, lemon, and sugar to a sterilised jar, then pour in the water. Stir well, seal with a lid, and label the jar with the date.
Leave the mixture to ferment at room temperature. Each day for the next 5 days, “burp” the jar by briefly opening the lid to release any built-up gas, then re-seal. This prevents excess pressure from building up.
After 5 days, you’ll have a fizzy turmeric bug with a yeasty aroma, similar to beer or bread—signs that it’s ready to use. You can use it immediately or store it in the fridge, where it will keep for around 1 week.