A couple more videos:
The fallow display tank:
https://www.youtube.com/watch?v=-w3soi4hkLM
A couple Harris Mud Crabs (Rhithropanopeus harrisii), one of two species in the tank. I always thought that these were a nasty muddy brown when collecting them in the field, but in a tank, they "clean up" really nice, and I find them quite attractive. They are very secretive though, but during the fallow period, when the fish are away, the crabs will play.
https://www.youtube.com/watch?v=lRMXr0LUz6c