But the white stuff isn't a problem or mold. Just mix it in, that is yeast growing. Had it come on one of my batches and thought the same thing.Had my lid airtight.....That's what I did wrong then. They love FF and I've watched it bubble and brew and smell like beer, but today, the white film had some sort of fur growing. I stir it up daily when I add or take any. Today, I scraped the skim off the top & fed the rest to them. They were in heaven!![]()