Basically this is simple...
If you are breeding almost any species fish, when they are about to breed, breeding, and tending to the brood....THE FISH WILL BE AGGRESSIVE to WHOEVER POSES a THREAT to THEM AND THEIR BABIES. (Not alwayyyyys true tho)
Fish get pretty aggressive when they breed, and usually you realize it when its too late and you either have a beat up fish, or a dead one.
Festae Grow kinda slow tho i think, but can get around 10".(Male)
MY convicts are VERY VERY aggressive when they breed, my 2 inch female beats up a 6.5" Male JD and his partner.