Thanks Steve, I agree, very strange. No prazi. PB had not been reclusive at all until this morning when it was hiding in the PVC. It's now out (as the photos show) but only showing a tepid interest in food. I had not been able to get it to eat nori at all, so I wonder if it might be some kind of nutritional deficiency? I'd been feeding lots of spirulina brine as a way to get it some algae in addition to mysis. Both were gobbled down with enthusiasm (unlike the evansi which are picky as heck).
I may just try CP. Going off in a business trip for a few days, so need to something that won't require close monitoring.