bang guy or other bangaii experts help!

[opazen]

i did a silly thing and i bought two bengaii on a whim... this is not common practice for me but the two seemed to be freindly towards eachother so i bought them. later i found out that they were only recently put in the tank at the fish store and i found the two, or rather the larger of the two to be very agressive. So i exchanged him for another hoping on the 50 50 chance it would be a she. The question is for experts because i hear that it is difficult to tell. How do you --- your bengaiis? I read that it was something in the jaw but i dont know what to look for. To complicate things i have to go out of town so id like to resolve this problem asap. the replacement bengaii and the other are on opposite sides of the tanks as i type so i dont know what to do.
thanks in advance
adam

 

[opazen]

thanks for the reply... the agression that ive been seeing is one fish chasing the other, and it has only been in the tank two hours. so i believe i will have to separate them ... now here is another question. Now that one or the other will be in the tank will introducing another cause a problem. i was of the impression that i was to introduce two or more simultaneously. should i get rid of both and try again with a group of them?
thanks
adam