well my gts are like 2.5in and i think a pair is forming between them because i will see them swimming together and then i see them both (at different times not together though) chase off the spare female i have and when they do charge at each other they end up swimming in little circles, what your saying sounds more like fighting but do they also swim together when not fighting? and do they swim in little circles around each other (without flaring) if you could get a vid of their behavior it would be easier to tell but pretty much if it doesnt seem like they are trying to kill each other or are always pushing the other one out of their area then its possible they are a forming pair (do you know if its male/female yet? dont know anything about firemouths so dont know when you can sex them)