cutteri cichlid pair not getting along

so I had 7 cutterI cichlids and I noticed that my biggest male was hanging out with my biggest female so I sold the other 5. now the male is chasing the female and nipping her. his colors are really bright and beautiful while hers were really blue and pretty and she had a black "beard" before I sent of the other ones now the female is very light. I add a lot more rocks to give her more places to hide but what else should I do? will they need to be seperated? theyre in a 20 gallon long. I can post pics of the setup and fish if needed.
thanks

 

anyone?

 

so what I'm seeing is that the male will come up in front of her and tilt his body down at her like this / and then chase her. she could hide if she wanted but she chooses not to. what should I do???

 

seriously??? no one??

 

Sounds like mating behaviour.

 

whys he chasing and nipping her though?