It is not uncommon for a kombucha scoby (symbiotic culture of bacteria and yeast) to sink to the bottom of the brew jar during the fermentation process. The scoby is a rubbery, translucent disc that forms on the surface of the sweetened tea during the fermentation process and is made up of a combination of bacteria and yeast that work together to convert the tea and sugar into acetic acid and other compounds.If your scoby has sunk to the bottom of the brew jar, it is not necessarily a cause for concern. The scoby is a living organism and can sometimes become detached from the surface of the tea during the fermentation process. As long as a new scoby is forming on the surface of the tea, it is a sign that the fermentation process is on track.It is possible for the scoby to sink to the bottom of the brew jar for a variety of reasons, including:The scoby is old and has become too heavy to floatThe brew jar is too large and the scoby has difficulty staying afloatThe scoby is too thin and has difficulty staying afloatThe scoby has become detached from the surface of the teaIf the scoby has detached from the surface of the tea and is floating freely at the bottom of the jar, it may be dead or dying. In this case, it is generally recommended to remove the scoby and start a new batch of kombucha with a fresh scoby.Overall, if your scoby has sunk to the bottom of the brew jar, it is important to carefully observe it and make sure that a new scoby is forming on the surface of the tea. As long as a new scoby is forming and the fermentation process is on track, it is okay if the scoby sinks to the bottom of the jar. However, if the scoby is detached and appears to be dead or dying, it is generally recommended to remove it and start a new batch of kombucha with a fresh scoby.