Strange behavor

[dwsindy]

Is it normal for your fish to come to the top of the tank and gulp air? My one spot foxface does this almost every evening after supper and continues until lights out. The other fish in the tank are fine. Could there be a loss of o2 by the end of the day? He is the biggest fish in the tank. Probably 4 1/2" long. There is only 5 fish in the tank (125). 2 small clowns a small copper band butterfly and 3" dejardini tang. Thanks

 

[ColeBC]

My orange shoulder tang does that too. Every night when the lights go off, he starts this thing I call munching. For the longest time I used to think he was gulping air but one day I realized he eats something from the surface. It might be algae or something growing on the glass or the stuff on the surface.
He's really loud when he does it and it always makes people laugh and ask about it.
This might not be the case with your fish but I thought I'd let you know what my tang does.

Cole