i recently added a light to my 120g tank and since this morning one of my barbs is constantly staying at the surface of the tank as if he was feeding off of it but hes been doing this for a few hours now, i also had to remove the air bar i had in the tank to operate a filter i put in there to replace an elcheapo filter that died. is the barb staying at the tank because it needs more oxygen? if so how come the other 13 fish in the tank aren't doing the same, any help on this matter is greatly appreciated.