I wanted a pretty scoby, too, so I brewed batches with every kind of tea I could find at Kroger this winter. What I found to make the prettiest scobies was plain green tea. I left it in for 28 days and the result was a beautiful, blemish-free, off-white scoby about 1/3 inch thick. I can recreate these beautiful scobies any time I do this. The problem is, though, that the kombucha is so sour that it is nearly vinegar. In fact, in just a few additional days, it is as sour as apple cider vinegar (regular, not Bragg's with the live cultures included -- that is far sourer). We cannot drink it that sour. In 10 days, the scoby is beautiful, smooth, white and blemish-free. It is only about 1/4 inch thick, though. If I start another batch with the scoby, it usually stays just enough below the surface to allow a new scoby to form unattached to the original one.
So, basically I can have either thick pretty scobies or great tasting kombucha that we can drink, but not both. What we did with the sour kombucha is fill botles half full, then fill them the rest of the way with newly-made tea of various flavors (regular teas and herbal teas) and allow them to complete second ferments. In 3-5 days, the new tea had fermented into delicious sweet and sour bliss.
So, the too-sour kombucha wasn't wasted. I used some of it to make vinegar for salad dressings, cole slaw dressing, etc. In fact, I grated cabbage, carrots and peppers and fermented it with kombucha for 3-5 days, then drained it and mixed it with a cole slaw dressing I made from kombucha and thick, strained milk kefir, herbs and spices. It has kept in the fridge for a couple weeks and gets better rather than spoiling like regular cole slaw.