A question of (brewing) balance.

[Guest guest]

If I understand KT, its fermented by way of two symbiotic organisms, a

yeast and somthing else.

The yeast is the brown areas and thready stuff, while the other

organism is the off white slimey stuff that accrues on the surface of

the tea.

From brew to brew it seems like sometimes the yeast predominates (and

the brewing process is quite fizzy, resulting in a thin scoby, while

other times its not so fizzy if at all, and then the end product is KT

and a much thicker scoby.

What affects this dynamic and how does one attain the optimal balance

of the two organisms over the course of brewing?