Why is my German Blue Ram so mean?

My male GBR chases my female GBR across my tank and then goes back to his little corner. I know he is a male cuz he has no pink spot on his stomach and he has no blue sheen in his black spot. I also know I have a female cuz she has a pink spot and she has the blue sheen. Why is he so mean? Please no copy and pasted answers just give an anwser that is specalized to my question, not an answer from another site that is meant to be general.