Davy appears to be doing just fine. He's still wandering about the tank in the evening, but as with last week, he's not appearing to be stressed (at least to my untrained eye). He's also still eating.
I took a short video of his wandering routine (sorry for the bad video quality). The video is still processing so it might not be avaialble in HD just yet. Let me know if anything about this seems stressed or problematic:
Do you leave the blue light on all night? If so, try turning is off. It is thought that blue is actually worse than white light. In the past, we noticed one of ours wandering at night (O. hummelincki should be sleeping) and realized that our red night light had been reset with a power outage, causing him to miss his beauty sleep.
Thanks for the reply @DWhatley. His light is completely off at night. The room isn't pitch black, but it's pretty close. There are no moonlights on any of my other tanks. The only possible sources of light are things like the status LEDs on a Reefkeeper controller, an Ecotech pump controller, and a Jebao dosing pump. It's also a dedicated aquarium room with blackout curtains, so once the last light goes off (which happens to be the light on Davy's tank), the room is pretty dark til morning.
Does anything seem particularly troubling to you about the way he was moving in the video? That was probably taken around 8 PM or so, which is about two hours before his light turns off. Once the lights go out, he seems to be pretty stationary. I can always find him in his favorite spot on his favorite rock.
Thanks again for replying to this thread so regularly
Davy has not eaten for the past two days and refused food today also. He has also stopped roaming around the tank, and has gone back to perching on one rock and staying there.
The only change that has been made in the tank is with the light. The light was heavy in the blue spectrum, probably around 3% white, 5% blue and 10% royal blue. I changed the light to a more balanced 5/5/5 on all channels. He ate after that change, so I did not assume him to be bothered by the lighting change. I've since changed the lights back.
I performed a ~10% water change (5 gallons) the first day he refused food. The second day (yesterday), I got a bit concerned and did a 25% change (10 gallons). I'm not sure what to do now that he refused food for a third day. I tried actually taking the piece of shrimp to him and touching his arm with it, but he just shot water at me.
Does anyone have any ideas what might be going on?
As you are trying not to guess, this may be the beginning of senescence. You can try offering smaller pieces of food. If you are hand feeding, try using a feeding stick and placing the smaller piece close to the beak. Sometimes this helps stimulate an interest in eating. You can also try putting a small live crab (fiddlers work well and can often be found in pet stores when you only want one or two - online is way cheaper for regular feedings). I gave ET a piece of raw fish yesterday (tuna I think but I keep a few small pieces of raw fish vacuum sealed and frozen to give a change of food options when they tend to not eat well. Also, check your salinity. Even though I have been using the same brand and mixing the same way for years, I found my salinity was low in all my tanks last week.