question on why my fish does this

Question
why does my fish dig in the rocks and swim fast around the tank

Answer
Hi T;

What kind of fish is it?
How big is he?
How big is his tank?
How long has it been set up?
Do you have other fish?
What is the water temperature?
What kind of filter?
How long have you had him?

Let me know as soon as you can...

At Your Service;
Chris Robbins