Neal- if you remember from our class with Carl Weese, periodically you should filter that stuff off that separates, and replenish with fresh developer. I've forgotten once or twice and then when I poured well-saturated developer over a fresh print, I got all these little thread-like things floating around in the developer. They all come off in the wash, but it's distracting because you're never quite sure until they're washed if one of them is a flaw in the print or if it's just the thread.