problem with kribensis

I recently bought 2 kribensis a male and a female for my 20 gallon tank. About 3 days after getting them the female started constantly chasing and nipping at the male. It got so bad that he would lay in a plant and not move. I put him in a breeding net I had for 3 days and he started acting fine swimming so I let him back in and she went after him again. So right now she is in the net and I've rearranged the tank. While he was in the net her color disappeared till she saw him in the net and then it got a real dark purple. What can I do to prevent her from chasing and nipping him?
=== My Quick Help Info ===================

Tank Stats
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Size of Tank (Gallons / Litres): 20 gallons
Running for how long: little over a month

Water Params
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Temp: 79
pH: 7.0
Ammonia (ppm): 0
NitrIte (ppm): 0
NitrAte (ppm):when I check it's 40 and then I do a water change
Water-change Schedule: once a week
Water-change Amount: 4 gallons
Any Water Additives: just the declorinator

What fish are in the tank, length, age, etc.
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2 kribensis male and female. He is about 2" and she is a little over an inch and a half. Not sure on age
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Nope when I rearranged the tank I moved the cave expecting that could be it but nothing. It doesn't matter where he is in the tank she finds him and attacks. Now with her in the net he is trying to attack her through the net.

Unfortunantly I don't have an extra which is why I got her in the breeding net. What's weird the first 3 days they were close to each other first in the plants then she went in the cave and he stayed right outside it.

Do you think if I keeping separating and putting them back together they'll eventually get along or will I need to exchange one for either another male or female?

I put him in the net Saturday because he looked like he might die. I released him in the tank yesterday and she bit a piece of his tail or at least I think she did it. So yesterday I put her in the net and rearranged the tank. He seems happy but she seems very lonely. It got so bad with her that he was vertical in the plants sometimes turning sideways. I honestly want them to get along and not have to exchange either of them.