payara aggression prob?

[cudamaster13]

my largest red tailed payara is becomeing a bit more aggresive lately for instance he bit two huge holes in my spotted silverdollar but the silver dollar is healing now but was wondering how i can get him less agro as well as get rid of some of the aggresion between that payara and my yellowtailed barracuda?

 

[Arowana1]

I have been seeing and hearing that Payara are similar to Arowanas when being kept with the same species. If you have got 2-3 Payara some fighting happens. While if you have got 5-7 not much fighting happens. Has anyone else noticed this?