Well, its been almost a week, and I still have had no positive sighting yet.
I did put in a raw shrimp I bought from the grocery store today. My red serpent star immediately came out of the rock to grab a piece, but I didn't see the octo.
On the time lapse video I did see something move about one of the tank decorations. It was in the back, and not in focus, so I couldn't positively ID it. I would have thought it to be a hermit crab, if I hadn't removed all of them already (to avoid confusion with the time lapse). It could have been a large amphipod. It didn't really look like an octo, but then again, it wasn't in focus and didn't look like anything but a dark blob. But, something was definately there and moving. So, I've repositioned the camera and am hoping to get another glimpse of whatever it was.
-Warren