I’ve been brewing for a few years and I’ve never seen anything like this. I prepared a 2-liter yeast started and pitched it on Friday into a typical Irish Red Ale. It bubbled normally for the first day, dropped off significantly on the second, and stopped altogether on the third. In all the times I’ve brewed before, bubbling slowed by the second or third day and never stopped until I moved to a secondary. What’s wrong (if anything) and what should I do?
Without knowing more about your beer, OG, fermentation temp, etc, can’t really say…
A 2 L starter is a pretty hefty starter so it could definitely finish up a beer in 3 days, especially if fermented warm.
Airlock activity is no sign of anything other than the release of CO2. Have you taken a gravity reading? Maybe it’s at FG.
Fermentation temp was around 70 degrees and the OG was 44, I think. I was working with a yeast packet that was about 5 months old so I made the large starter just to be safe. I’ve done stuff like this before, though, and always it continued to bubble, admittedly at quite a slow rate (around 1 or 2 bubbles per minute) until I moved it to the secondary. I’ve never had it just completely stop before.
Take a gravity reading, maybe it’s done. At 70 the beer will ferment pretty fast, and if you poured in an active starter, the lag time could be minimal. Can’t really determine what if anything should be done though without knowing what the gravity is at now.