I wondered about the dish vs. sponge thing. When I read this sticky thread:
http://www.cigarasylum.com/vb/showthread.php?t=620
the original poster spoke of the dish of distilled (yup, I did use distilled) water, so I went with that -- and during my sporadic peeks, this was not something that popped up instantly. My thinking (like Fordman) is that it might be mold; for the time being, I've dumped out the water and replaced it with a clean dish.
Here's the picture from just now:
You can see the ring, obviously, and the slight flecks in the water.
At this point, the hygrometer's reading the RH that I want, but I wanted to give it another couple of days just to keep things good until I throw some Humidipaks in there. At this point, would dish vs. sponge even matter?
If this is truly mold, as I'm beginning to now think it might be, perhaps that would be the main caveat for NOT using the dish method.