Well, for an update, I've done a ~15% water change Tuesday, and will do one today (every other day, basically) when I get home, and will actually end up with more water changed per week. So far this week, I think I saw a one dead Monday morning as I was leaving for work, but I couldn't find any sign of it when I got home. I've also found some encouraging signs. I found a molted shell Monday night and this morning, *and* I saw one of the large females is berried this morning.
The polyfilter still hasn't changed color noticeably, so I presume that means I either got a defective product, or there isn't enough of anything it measures in high enough concentration to cause any color change that I can see. It's in the filter, so it's definitely got water going over/through it. I'll give it till next week before I get too worried.
Saw 14 last night, but none of them were the big (now berried) female, and saw 10 this morning. Still don't know exactly where they're hiding, but there are lots of options, including under the driftwood or in the java fern, let alone the hiding that can be done in the peacock moss.