The tank madness continues! I'm wondering if I have a hitchhiker pistol shrimp. That would actually be pretty great. I've noticed this a couple of times in the last week or so. It always happens at night. I just might have to pull out the red flashlight and do a little nighttime spying.
I have some kind of earth mover, pushing the sand around at night. The only thing I've ever seen do this before was a pistol shrimp. My only "sand dwellers" are the large Tongan nassarius snails. They just pop out of the sand when food arrives and go right back in. I have a yellow WM goby. He will do some sand sifting, but never to this extent (and not at night). The powerheads haven't been moved, and if it was a powerhead, I would expect sand blowing around (and why does it just happen at night??). The Kole tang is kind of pointing at it.

I guess for now, the mystery will continue!