so here's my scenario. I set up a 3.1 colony 2 months back. The rats are now probably around 3-4 months old now, no signs of babies but the colony seems to get along fine and I sometimes put rats that my snake refuse in this colony temporally and they seem to accept newcomers just fine.

Now the impatient me is thinking maybe the male in my first colony is infertile thats why i'm not seeing any babies...so today I look on kijiji and someone is giving away a pair of adult males rats (according to the ad 6 months old and has been living together with each other since babies). So i went and pick the two boys up and set them up in a new tank. I read somewhere that 2 bonded males wont fight over females.... sooooo the impatient me here drop 2 of my females rats (which is half the size of the adult males) into the 2 males' tank. Immediately the males start beating the crap out of the two females, by the time i finally got to seperate them the two females are already bloody all over...

now the two female is back in with the original colony (I feel so bad)

and

the two newly acquire male now wont stop fighting with each other..... one of the male is clearly more aggressive than the other male and beating on the other one every 5 mins. like full on aggression with the hair raise and teeth chattering. The one being beat on is so jumpy now even a slight touch will sent it into defensive mode...

I don't know what to do, my plan was to have only 2 colonies and now i have 3 male, 1 seems to either infertile or too young and two that no longer gets along with each other and seems to want to kill the female in put in with them rather than mate... any advice?