new 10g for my occies

I just set this up for my occies, figured id give them their own tank and see if theyll breed

yeah, its black moon sand mixed with a little grey and white gravel, there are 5 in there and i went to put a small java fern in the tank and i was attacked by the largest one. Kinda humerous but im wondering if this is a normal sign of territorial aggression or if they may be breeding in there already? i've noticed the largest occie displaying to a couple of others but their has not been hardly any aggression amongst each other.