Is this a mating ritual, aggression or territorial ritual? 
Or what? 
 
I have two big dats, 1 foot + 
Both in same tank and been raised together since small.  
 
I noticed a few things, please tell me what they all are:D 
 
1)	twitching o the dorsal fin, rapid opening and  closing them 
2)	shuddering body, shaking it like a person shaking his ass.  
3)	Clapping its mouth 
4)	Like a person making sounds with their teeth, by opening and closing rapidly, you can actually hear it from outside the tank the clapping of the mouth 
They both d it, one does I, then the other does it. Stretching the mouth they extend the mouth way out and all their fins then close it again 
 
At first I thought it was an itch, but that’s seld explanatory, they itch and scratch with gravel 
But the above, are all a little different 
Any ideas?