I have one that does the same thing. Moves up/down; out an then under a rock. Has done this for a few weeks since I got it. I have very few fish and only a few corals in a 75g and 30g sump Oh yeah ~ 75lbs of LR. I have plenty of pods running around so it should be eating them between my 2x wk feedings of mysis. I am with you, I have no idea what do although I just keep waiting for it to be "happy". I too have adjusted lighting durations although never to the point of major off-times, except during the overnight (6 hrs all-off). I will keep looking at your thread for any suggestions other than taking the "hands-off" approach.
Wise Ones of the R2R Forums:
Is it possible to have too clean of a tank? Anyone have any ideas - Here is what I can measure: no measurable h2o issues (NO4, NO3, NO2 all 0); pH 8.1, temp 78.5-79.2. Salinity 1.026. I use RO/DI with weekly 10g changes. Tank has been up x 7 months. All tests are very stable...hence the reason I thought it was time to try a RBTA. I virtually have no algea anywhere - small rim line and some in overflow otherwise zero algae.
Other info: LED strip with total of ~ 80w with 0.5w LEDS with the following breakdown. 84x White 6500k; 56x Blue 460; 9x Red 620; 9x Green 525nm and 10x 0.5w Actinic 465nm for moonlight look. I also run 2 4ft T5s 10000k during a 12 hr day cycle.