I have seen similar behavior in my tank but it usually stops once the pair settles on a territory. If you do not have breeding caves, large shells, or something to assist the pair they might continue to bicker until they settle in.
I had a few spawns in a 40 long, but the fry are hard to keep alive. I put my quad in 1M/3F in my 125 with my Gibberosa kitumba. They don't fight as much with a 6ft tank, but they are conspecies aggressive by nature.
Just keep being watchful, get some breeder caves or shells and they will eventually settle down.