For sure. I use opaque plastic now, but I started out on glass carboys and I remember the Belgian abbey yeast I used going absolutely insane, generating tons of heat, clogging up the airlock, and sending foam all over the inside of my Cool Brewing bag. The inside of the fermenter was practically churning. Since I used transparent fermenters for quite a few years, I don't really mind using opaque ones now (my main fermenter was a Speidel for a while as well), but it's definitely interesting to watch.