Well, I was worried that I might have had a stalled, or stuck, fermentation. The regular belching of the blow-off tube in the sanitizer stopped without warning. I didn't see any bubbling at all in the sanitizer so I replaced the blow-off tube with the airlock. That has been bubbling--slowly. On closer inspection, I can still see bubbling on the edge of the carboy, but I'm still a bit concerned that fermentation may have slowed to a crawl. I was set to pitch more yeast, but that was probably premature.