Everytime i've tried pairing my rhomboids something terrible happens , i originally introduced a harem of 3 , 1 male 2 females , one of the females didn't make it. The other female turned male. Eventually (3-5 months later ) the dominant male killed the other male .. Second time, the female turned male in a few days, and once again the larger male killed the other male... Hope you have better luck than me. My male is quite large though around 5-6 inches , even dominates my lineatus which one of them is over 6inches without the tail .
The picture above, looks like a full male now.. Females look pale and have almost no blue/purple in the facial markings . Also the lower fins are already showing color. If your seeing this much aggression, you should also see them flash ... also this is usually the time they think of jumping due being chased so if you have not covered your tank , now would be the time.