Our marshmallow porter seems to have some type or mold or sediment floating atop the beer after 17 days fermenting in a wide-mouth plastic carboy. They look like flakes. Not fuzzy or spider-web like. Beer tastes and smells similar to usual, Preconditioning, but we’ve never had floaters like this before. Should we toss it or is it fine to bottle?

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  • Some beers are made from mould and mould is penasilin
    – Fatash89
    Commented Sep 29, 2021 at 19:26
  • Over the years I have seen some of my brews look pretty horrifying at various times and come out just fine. It's worth reminding yourself that what you're doing is an organic process. It often isn't pretty.
    – Mr. Boy
    Commented Oct 25, 2021 at 20:10

2 Answers 2


Unless whatever you're bottling is genuinely, horrifyingly undrinkable- I'd never pour anything out before bottling. At any rate- it won't hurt you.

It's really difficult to tell on a picture through a carboy- but it's probably normal coagulation of some oils and starches in your beer.

The rough picture may have some folks tell you it's a lacto infection- but based on the patterns and color I'd say that likely isn't the case.

  • Thank you, Rob! Commented Aug 4, 2021 at 17:03
  • 3
    @RyanO'Connor: These are islands of yeast floating on top of your wort. The color is correct, and the shapes are what I know from brewing too. Maybe that with the addition of the marshmallow the yeast clumps easier together and stays afloat.
    – chthon
    Commented Aug 6, 2021 at 14:30

Looks like "yeast rafts" to me. In other words, normal fermentation.

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