Clownfish on side at surface

[aaclown]

I have had this clownfish for over a month and it has always swam near surface and never been to the bottom of the tank. It has recently been on its side a lot near the surface. I attach a video. The ammonia was a out 1 today so I did a 40 percent water change. The other parameters all seem alright. I'm worried it is not well as it's movement has decreased and increasingly on its side.

 

[kitti-fish]

Having a hard time seeing the video but from my experience clowns are really weird. Mine likes to swim on their side, swim upright, and just hover around wavemakers acting weird. Is it otherwise eating normally?

 

[Fish Fan]

Did you stop the flow in the tank for the video? If not, I would say that this is likely low oxygen, and the tank needs a lot more aeration.

Also, the tank looks very new, was it cycled for nitrogen before adding the fish?