How do i get my male koi fish to leave my female alone?

Ok So my male and female Koi fish are both best buddys they stick by each other through thick and thin and don't like to leave each other but this morning i woke up because i heard splaching at the top of the water and though my fish were just being annoying so i tried to ignore it but when it kept happening i got up and added a little more water to the fish tank to shut it up and quiet my filter because i don't like hearing the water at night. I was doing research because i though that there might be something wrong with them and i found that in breeding times the male will chase the female. Ok that's what seems to be happening with mine but i don't see any eggs and it's winter time plus they are both still eating so i don't think they're sick but i don't like him chacing her until she tries to get away from him at the top of the water and hetting herself on something to get away. she is realy pretty so i know how she looks but watching them i noticed in the time it took me to go from one side of my house to the other she is ow missing scales because he will whace her into a corner and when she goes up to get away this particular corner has the filter in it so she scrapes against the filer to try to get away. she is about 7 1/2'' long and about 5'' wide and he is about 7'' long and 3-4'' wide. as you can see they are small but that can be atributes to living in a tank so they wont get any bigger and they are about 3 years old more or less. Help please and no i can't get a pond where i live it's not possible at the moment