Moving gravel into piles

Hi, i'm new and just wanted to ask a question. What does it mean when a fish is taking the gravel on the bottom of the tank and moving it into piles, leaving the bottom of the tank exposed?

 

what kind of fish are they? If they are cichlids then it is normal. Cichlids love digging. ;D

Joe

 

If your fish are cichlids, this is typical breeding behavior, and they are digging pits.

 

You might be lucky and find some baby fish in your tank soon!

 

My multi's have hit bottom in spots too! The mountains and valleys the build are marvelous! Enjoy!