I haven't brewed it in a few years, but my first batch ever wound up getting mold in it. I'm not really sure why, or how, the rest of my batches were fine.
It was very obvious, it looks like just the white/green mold that will grow on top of a drink if you leave it out.
edit: Oh, the scoby is always obvious, it's basically a gelationous alien looking thing that should star in Xfiles. Every few weeks the scoby will split off and you'll have multiples, you take out the second one and can give it to someone else or make a new batch.
It was very obvious, it looks like just the white/green mold that will grow on top of a drink if you leave it out.
edit: Oh, the scoby is always obvious, it's basically a gelationous alien looking thing that should star in Xfiles. Every few weeks the scoby will split off and you'll have multiples, you take out the second one and can give it to someone else or make a new batch.
https://www.kombuchakamp.com/wp-content/uploads/2012/04/5-Si... -- the white thing on top with "laywers" is the scoby. The layers detach every so often and become independent.