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Hitting final gravities

TroubleShooting

Jason Manzano asks,
Q

I cannot seem to hit my final gravity on any of my brews. I just finished a stout that should have gotten down to about 1.020 specific gravity even with the roasted grains, but it stopped at 1.037 after two weeks. I am aerating my wort with an air pump and air stone, I am using a yeast starter, adding yeast nutrient, and using a temperature-controlled freezer with a conical fermenter. I don’t know what I am doing wrong!

A
This is a difficult question to address because there are some important facts that are missing, such as wort original gravity (OG), grist bill, mashing method, yeast strain and fermentation temperature. But
Response by Ashton Lewis.