To avoid mold problems, try continuous brew. You DO NOT NEED A SCOBY to start kombucha as many people seem to think. Here is the best procedure I've found, and it will produce a scoby before long.
Buy several bottles of plain kombucha, I use GTs. Pour them into an ice tea jar with a spigot. Preferably a glass jar, and add an equal amount of sweet tea. I use 4 tea bags and a cup of sugar per gallon.
In about a week, your kombucha will be sour. At that point double it again. You can add less if you don't need to double it to fill your jar.
Repeat until you have your jar full.
Once the jar is full, and sour, draw off about 25-50% and replace with sweet tea. DO NOT HANDLE THE SCOBY..... dump the sweet tea right over the scoby. This will sink the scoby, and tumble it around, and it will refloat in it's own sweet time. I like to do 25%, about every 4 days (I like mine fairly sour). The 25% procedure means that the scoby will get a good "bath" every 4 days or so, and will refloat with a very acid surface which will prevent mold growth.
The scoby will eventually get thick enough to be inconvenient. Simply fish it out and throw it away, a new one will begin to form fairly quickly, and within a couple of weeks will be pretty respectable.
The scoby does NOT make kombucha, rather it is produced as a byproduct of acetobacter souring, and is merely a mat of biocellulose. It is NOT a living organism.
It is also NOT necessary to have a cloth cover over your kombucha to allow it to "breath" if you are doing continuous brew..........There will be plenty of oxygen introduced each time you add sweet tea. I've done this in 6 gallon brew buckets with the lid snapped on tightly, and brewed well in excess of a hundred of gallons of kombucha, as I was supplying a friend who owned a microbrewery so he and his employees had booch instead of beer to drink.
H.W.
H.W.