I've got a Vienna/tettnanger smash in secondary and it has this odd black hue to it, isolated to the top couple inches. I've never fermented in carboys before, so I'm not sure if this is just an optical illusion? I used kolsh yeast which still has a tendency to not flocculate so well, from my research. So I chose to secondary after about 4 weeks in primary. In the secondary vessel, it seemed as though after appeared to clear with flocculation this dichotomy appeared where the top couple inches appear much darker than the rest of the carboy. Any thoughts?
Never attached a picture before, hopefully this works. I'm not sure if this picture does the phenomena justice either, but this is what I'm seeing.