Here’s her set up, so you can see the size of scoby she uses per jar.
My girlfriend normally makes around 3 litres per week across 2 kilner jars.
She uses a ratio of 8 green tea bags, 300g white sugar, 3-3.2 litres boiled water (can scale up/down). Steep for 10 mins and teabags out. Let it cool. Once cool, bottle last week’s batch (see later). Leave about 200ml old kombucha with the scoby in each large jar and top up with 1.5-1.6 litres cooled sweet tea. Cover with kitchen towel/rubber band.
This might be overkill, but on alternate days she dampens the kitchen paper with white vinegar during the week to prevent mould.
Bottling: After bottling you can either leave them at room temp overnight and refrigerate next morning, or you can drink them straight. You need to ‘burp’ the bottles daily at room temp to avoid explosion.
Flavouring: add your flavours to the bottles when you’re bottling. For 750ml bottle, she’s used juice of half lemon or lime plus 1inch of ginger in matchsticks. Or 4:1 ratio kombucha to fruit juice. She’s also used peeled plums as well.
She’s used these websites for advice: https://www.culturesforhealth.com/learn/kombucha/kombucha-tea-frequently-asked-questions-faq/