Hi,
I have kept festae for nearly 3 years and can confirm that I have found them to be 'assertive' all the time and mine were straight out nasty once they had paired and had eggs in the tank.
By assertive I mean mine would chase and nip other fish entering their territory but retreat once they had backed off. whereas once there was eggs the male and female would chase and chase and bite all day (till I removed them).
They only fought each other at 3 inches, at 6 inches other tank mates were being 'moved along'.
Once they were larger and there was only the pair of festae (no other festae) they were a heap calmer but when they spawned they were nuts but not killers just serial nippers.
I would recommend keeping them in a species tank with maybe some big silver dollars for dither fish.
Watch them at breeding time, my male tore a 1/2 inch hole in the side of his mate coz he was ready and she wasn't ....
Here are mine:
View attachment 469519
View attachment 469520
Good luck, they both look absolutely beautiful when breeding!
J
