Flame Angle question

[cdh9400t]

Hey everyone, this is my first flame angle and I’m questioning something it’s doing. It keeps going in the corner of the overflow at the back of the tank, shakes its tail fast to move the sand substrate. Not sure why it keeps digging a hole, but wondered if this is something normal they do. The rest of his behavior seems good. Eats good, swims through all the rock tunnels like a race track. TIA.

 

[exnisstech]

I've had my flame angel for two years but I'm bare bottom. I've never seen any strange behavior, it just cruises around in the rocks all day.