Betta playing or chasing reflection?

[chub04]

It might be hard to tell, but I wanted to know if my Betta is just playing or is it stressed and chasing its reflection? Here's a video:

I'll try to get a better video later.

Water parameters are good for the most part.
Ammonia-0
Nitrite-0
Nitrate-10
Ph-7.8

My tap is naturally high in Ph so I'm working on lowering it, but that was the Ph of the water the Betta came in.
Water temp is 79 degrees

He's also building bubble nests, does that mean he's happy?

Thanks!

 

[chub04]

He seems healthy, just wanted to make sure he's not stressed or anything. And if he is chasing his reflection how do I stop that?