My scoby (symbiotic culture of bacteria and yeast) is getting leggy. I think it's about to add another layer to itself. The top layer is actually rather leathery since it has contact with the air. The ones bottled up are into their second ferment which is only a couple days, or to taste. Longer = more acid/vinegar. Second ferment adds a little sugar for the food source, then in the sealed bottle the carbon dioxide has nowhere to go. When you open the bottle it's fizzy and carbonated
Nice! We found couple of those bottles at a secondhand store, I'm planning on maybe trying them with my next round of water kefir. So far I have just been pressurizing in the ball jars, which works okay, but it's not really sealed.