If I only want to prepare 1.5l of kombucha, do I have to divide the scoby?Updated a year ago

No, you can add the entire tea mushroom and half the amount of liquid. However, it is possible that your kombucha will be ready a little faster. So it's best to taste your kombucha after 5 days to see if you already like it. Then you can bottle it and start the secondary fermentation, which also produces carbonic acid. Keep in mind that it will still sour a little in the bottle.