heavy breathing but no sign of infection on percula

[h2o]

Problem started yesterday after i was going to feed my tank, my large percula had a shock and swam everywhere, inside lr, up and down, don't know why. He is emotionally attached to my flowerpot, wouldn't let anyone go nearby it, which i know is normal, but not heavy breathing, and unwilling to eat.
This fish has been in my established tank 6 months, has been healthy. i checked water parameter again this evening, phosphate 0, nitrate also 0, and calcium at 550ppm. No white spots, or anything infection on its body, what can be the cause of heavy breathing? internal infection? thank in advance

 

[h2o]

well......tonite the fish disappeared in tank, no where i could find it after one hour searching.

 

[broomer5]

Not really sure.
Calcium is high which I wouldn't think would be a problem, espeically if all other inverts and fish are doing okay ..... are they ?
Missing a large fish could be a big problem if it's dead .... decomposing fish flesh and ammonia production, you know the drill.
How's your water circulation ?
All other water parameters good as you said, including pH and temperature ?
Sorry I can't answer any disease questions - just trying to help here a little.