Why is my cichlid rearranging his tank?

Why does my cichlid keep picking up the rocks that cover the base of the tank? It is reshaping the aquascape of the aquarium constantly. Is there a reason for this behaviour?

JOANNE LACEY, VIA EMAIL

JEREMY REPLIES: Lots of cichlids dig, and this is primarily to create a territory to entice a female over, where they will then spawn. For mouthbrooding African cichlids, the female is then chased away, but with substrate spawning South and Central American cichlids (and some Africans) the pair will then use that pit as a nursery for eggs and fry and defend it.

It's not unusual for cichlids to bank the substrate up against the front glass to try and hide any activity away from you, the viewer. Some lonely cichlids will dig down to the bottom glass and then stare at their reflections as if trying to pair off with a potential mate. But don’t be alarmed — what you are seeing is natural behaviour and it’s what most cichlids are evolved to do.