I need to edit, I have 9 mantis shrimp tanks...(2 O. scyllarus, 1 G. ternatensis, 1 G. platysoma, 1 G. viridis, 2 P. cilata and 2 G. chiraga).
I usually turn my lights on off from 2-3, both am and pm. I work nights, sleep until 1 or 2, and they have adjusted to this easily enough.
The O. scyllarus are active whenever I am around, day or night and they could be out-and-about.
-Ron