Swordtail at top of tank

[Fray]

Hi all. Does anyone have an idea why my swordtail hangs at top of tank a lot? She looks to be gulping air, not a constant thing, but a fairly often thing!

180l tank, cycled with
Water parameters 0...0...10 to 20.
Ph 7.4
Temp 23 to 24
I have a filter either end of tank, air stone in the middle and a koralia (at opposite end to where she is in vid).
I'm not really worried about it, more curious, as she's healthy, and cruises around happily, but she is the only one who does it and I'm sure there is enough circulation in tank ??

 

[connorlindeman]

What are your ammonia readings?

 

[Fray]

Ammonia 0
Nitrite 0
Nitrate 10
As I mentioned, she isn't doing it constantly, just more than seems normal. And she's the only one to do it.

 

[Kyshiara]

HMMM my guppy does this too...

 

[connorlindeman]

Interesting. I don't know what the problem could be.