A couple of months ago I started a batch of vinegar. The sugar water had fermented. I had racked it into a bucket and added the starter (I used Bragg's apple cider vinegar). It was moving along perfectly. It made the water tower smell like vinegar - not the greatest smell in the world, but it meant it was working. The mother created a nice film on the top and everything looked good. And then the towel that was covering it fell into the vinegar. That was just the beginning of a series of mishaps that finally resulted in the vinegar gnats getting into it, laying eggs and leaving their lifeless corpses floating in the liquid. The vinegar smell started to dissapate. Yesterday I finally dumped it.
I will try it again. This time I'll find a better way to keep the gnats out.