I know there are a couple long (really long!) threads on fermented feeds, but thought I would offer an easy to understand alternative. The point of this is to make the comparison of fermented feeds to sourdough bread as there appears to be a high degree of similarity. The process and chemistry of it all for the hopelessly curious. I get frustrated by all the posts and references that are long on benefits and very short on process. I'm a process oriented type of person. So start with this commonly referenced link on fermented feeds: https://tikktok.wordpress.com/2014/04/13/fermented-feed-faq/ Eventually the author gets down to the actual process of maintaining this ferment and then references what is called "back slop" used for the daily refresh. So it turns out this is the same process as building and then maintaining a starter for sourdough bread. In this light, what might be helpful is to offer up the Internet's Gold Standard for how to go about making a sourdough starter in the first place. The timelines involved and chemical processes. http://www.thefreshloaf.com/node/10856/pineapple-juice-solution-part-1 http://www.thefreshloaf.com/node/10901/pineapple-juice-solution-part-2 Crib notes version is when you start up a ferment from scratch, it is a two step process. The initial bubbles you see are not from a desirable bugs and yeast. Quite the opposite. There is an initial explosion of bacteria of the bad sort, and they do what they do and then create hostile conditions for themselves and die off. In doing so, they create ideal conditions for a second wave of bacteria and yeast that are to come later. In the pineapple solution, that is at least a 7 day process.......not 3 or 4 days as some suggest for fermented feeds. What pineapple juice does is to jump start the process to make the solution more acidic to begin with, so shortens the time involved. Not suggesting you use pineapple juice......the reference is simply there to explain what is going on. Water will work just fine both to start it and to maintain it. But still, process is this........after initial mixing you will experience: 1. Initial explosion of gas (foul smelling gasses from bad bacteria) 2. Dead Period 3. Renewal of activity leading to.. 4. Development of active starter (ferment consisting of good bacteria and yeast feeding on feed source) Second part of this is how sourdough starters are maintained. It is done in a consistent manner, with measured parts of starter, feed and water to refresh the thing. Probably a good staring place is equal volumes of the "back slop / starter", feed and water. BTW, in sourdough bread, the two byproducts of the fermentation process are CO2 gas and a clear liquid that really is alcohol. Technical term for it is "hooch". Ergo the name. In day to day process, the discard from this daily refresh is what you use to make your sourdough bread or feed the birds. You save some ferment, renew the feed and water and do it again.