your flame is pretty much full grown at 4inch , that's probably the reason for aggression
I always added angels young so there was no aggression , now back to your problem like bribo said you can try rearranging the rocks but that's not always 100% fool proof ,
going by the size of your flame he is a mature fish , maybe he was re-homed because he was being a trouble maker , with bigger fish that is always possible ,
flames are also more feisty and full of life never slowing down , I don't remember your tank size but maybe its to small , This could be what is bringing out the aggression by acting out that's his way of telling you I need more room ,
in all the years Ive had angel;s I never seen any aggression , This may be because I added them young giving them time to learn how to co-exist . you just never really know , fish are like us no 2 are alike each has it's own personality ,
I wish I could keep a flame as they are pretty fish my problem is the opposite of yours none of my fish like orange they always beat up on every orange fish I attempted , yellow , blue , red , purple ect no problems . strange but true ,
I got lucky with my clowns as they are a dark maroon with yellow stripes so no orange.
I have a orange sponge they are always tossing it around like a beach ball