I have two balloon mollies, one male and one female. I've had the female one in a isolation box, because I thought she was going to give birth for about three weeks now. But, she has not delivered. Just recently, I just bought some guppies to put in the regular tank with my male molly, but the male molly has been pretty aggressive towards the guppies. So, I put the mollies together in a separate 5 gallon tank. Once I released the female molly with the male one, she has been chasing the male around. It seems as if she's "nipping" him. Is this a sexual behavior, or just aggression from territory purposes?