leopoldi "hanging on the surface behaviour"

here,s a link to a clip of my leopoldi hanging on the surface,i wonder why they do this?
I know some members wrote about this behaviour before on this forum but i never really found out why they act like this.
It,s not a lack of oxygene cause i had altum in the same tank before and they never acted like this.

maybe they try to collect small animals(flies etc) from the surface?

Maybe someone knows..


re: leopoldi "hanging on the surface behaviour"

I see what you mean Andries, it appears to be a behavioural trait with the Leos. One contributor to the thread said that his Altum also did this. The excellent video that you posted showed the fish with what I took to be an accellerated breathing rate as they passed surface water And/or air over the gills. Could this be a behaviour to recover blood Oxygen levels after a bout of exertion? or to prepare for something that requires better oxygenation?, Digestion?