aggressive fish

Hi all
I have two fully grown Altum angelfish sharing a tank.
They are not a breeding pair yet!!!!
One keeps attacking the other all the time they have been together for 2 month.
I removed the aggressive one and replaced with a fully grown marble angelfish.
then the placid one started attacking the marble angelfish.
Are the silver striped angelfish just bad tempered.?
I have not been at it for long but find angelfish very interesting.
All the best.
Jim.

All angelfish will squabble to some degree as they establish a hirachy (unless you happen to have a well balanced pair)
I suspect your problem comes down to numbers.

With just 2 fish in the tank, the dominant individual only has one other fish to bully.
With 6 fish in the tank, there are so many possible interactions that it's much less likely that any one fish will be constantly picked on.