I have a stuck fermentation, what should I do?

There are a number of things that can lead to a stuck fermentation and sometimes its hard to narrow it down to which it was that has caused it to happen. It can be anything to do with the pitching temp, mashing process not providing balanced long and short sugars, grain crush not correct for brewing system, lack of nutrients in wort, lack of oxygen in wort, just to name a few things. At the end of the day the yeast is a living organism that relies totally on the right conditions and it needs food, oxygen, and the right temperature to do its job, and anything out of balance can result in a stuck fermentation where the yeast slows down or gets lazy as it runs out of one of these things.

If you are miles away from your FG then its still too high for bottling in my opinion as you would run the risk of having further fermentation in the bottle and having bottles explode.

You can try and number of things to rouse the existing yeast such as adding sugar and oxygen to the wort, or you can try raising the temperature slightly to wake it. Or the final step is to try pitching additional yeast, and in that case I would choose something like Nottingham or US-05 as part of a yeast starter depending on the beer style, and if that doesn’t work then I would consider maybe some Belle Saison but keep the temp at around 18c with this yeast.

It’s a big subject area and there is lots of information out there that is worth reading up on as it isn’t usually the fault of the yeast but down to process, check out this blog post.