I'm very sad, one of my female CPDs died, and I have no idea why. I moved the tank upstairs last week, which involved draining it a great deal, moving it, and then refilling it. I was pretty sure I counted all four last night when I fed them, but tonight only saw three, then I saw something stuck to the bottom of the prefilter. Particularly sad considering I was intending to move them all to the big tank soon.
Only other change recently is I added new BioMax filter media today, but that shouldn't do anything. I didn't remove the existing media, just added more.