male platy chasing female (mating or territorial or something else?)

[venzi]

Anyone know what kind of behavior this is?  The red wag tail male platy is chasing the red wag tail female (more like orange color).  The male doesn't do this to any other female bettas or platies in the tank.  It doesn't seem like a mating behavior.  More like territorial.

 

 

[FishRBeautiful]

I had a male Platy that chased all my fish but one specific (and I think infertile) Platy that was his own color he chased the most, just to be mean, not to mate. I kept adding female Platys and he only chased the one, all over the tank, even out of her hiding spots. But if any other fish of any kind came near him, he did the same thing, fin nipped them away. After lots of research, I decided he was a bully and surrendered him to the lfs. He’s still there and I’ve thought to buy him back a million times because I grew attached. He’s so pretty but so mean. But your video is exactly what mine did. I’m a new fish keeper so maybe someone else can chime in.

[Guppysnail]

I’ve had guppy boys choose one female they like the most and chase them about. 
If she is not showing signs of stress or nipped fins etc. I would not worry over the behavior. She may just be almost ready to breed and he intends on being the baby daddy. 
If she starts hiding a lot more, losing weight/color, not eating as much then I would worry. 
Some tall plants or decor through the center as sight breaks helps break up chasing for both mating and aggression.