I have a 180 with mixed peacocks (breeds and M/F's) in it, and usually don't have an aggression problem. But then there are the times when the Betta will test the Alpha and there is a heck of a battle and someone has to be pulled out, just had to do that about a month ago. The strange part is that they do not look alike at all, one is mainly blue and the other was pink/orange colors.