Angelfish Gulping At The Surface

hey all, my angelfish SushI seems to gulp for air all the time. Currently: Ammonia 0, nitrites 0, nitrates 5, pH 7.6, temp 79. (I do not know the hardness, I just ordered a test kit for that) I have a 60 gal tank, 2 airstones, proper filtration, 3 live plants... what could be causing this? He eats ok, he poops ok, and this seems to have been going on for a while. But he looks stressed and it's making me stress. Any ideas?

 

The only thing I can think of is lack of oxygen. The air stones and live plants should help but maybe not enough.

 

That's what I was thinking; except he is the only one doing it out of about 10 fish. he does it before and after partial water changes, 100% water changes, etc., so I'm not so sure if it's an oxygen issue

 

That's what I was thinking; except he is the only one doing it out of about 10 fish. he does it before and after partial water changes, 100% water changes, etc., so I'm not so sure if it's an oxygen issue

How large are the companion fish? Big animals require more oxygen. What's the tank's size? Small tank lose oxygen fast. Both of these don't seem entirely plausible, as 100% water changes would solve oxygen issues temporarily if the tank is too small. Maybe there's some sort of parasite latching on to the decor? It may be a disease, but I don't know any diseases that result in increased oxygen demands. I hope your angelfish gets well soon!

 

Thanks! Update: he’s still doing it....
I have a 65g (not 60 as previously stated) not much difference....
Ph, ammo, nitrites and nitrates all within normal limits.... kh and gh appear to be a bit lower that what they should be (about 50 ppm) so I’ve added coral to filter.... we’ll see what happens....

He is the largest of all fish... I have 3 angels, 1 boesman(sp?) rainbowfish, 2 dwarf gouramis, 2 small balance sharks, 2 pictus catfish, one red-finned shark, and 2 small “neon” tetras