My oscar having a brawl

[ASR]

My oscars are lip fighting with each other but as soon as I turn the lights of my aquarium on they stop fighting is it common for them or their might be some problem

 

[Gourami Swami]

It could be mating behavior or a squabble over territory. Oscars like all cichlids are territorial to a degree. What size is your tank, what size are the oscars, how long have they been together?

 

[Tony A.]

Yep we need more info.