Angelfish breathing rapid/ opening & closing mouth

[Oli]

Hi guys, I picked up a fully grown male Angelfish today, he is in a 200 litre tank alone which is fully cycled. I have noticed he is constantly opening and closing his mouth very obviously kind of every half a second. It is almost like he is breathing very quickly, as his gills also move in parallel to this. Is this a normal thing for angels? After glancing at my 60 litre tank, I have noticed my dwarf gouramis kind of do a similar thing, (though not as noticeably or frequently) perhaps it is just more noticeable on a larger fish? Besides this, he is eating fine and swimming normally and looks otherwise healthy. All Parmameters are normal. If someone might perhaps drop me a personal message I’d be able to email over a video of the behaviour. Thanks guys!

 

[Colin_T]

There might be something in the water irritating the fish and making it hard to breath.

Are you adding carbon dioxide (CO2) to the tank?
Is there any aeration/ surface turbulence in the tank?
Are there any other fish in the tank?

Increase the aeration to try and maximise the oxygen levels in the water. If there is no improvement after a few hours, do a 50% water change and see if it helps.
Make sure the new water is free of chlorine/ chloramine before it's added to the tank.

Check the water for ammonia, nitrite, nitrate and pH.

 

[Oli]

I changed the placement of the filter inflow to increase aeration a few hours ago and he calmed down and stopped doing it very quickly