I will also say sometimes young females will go to the top of the tank and gulp and hold air. I have seen this behavior in the past. Not sure why they do it as it is not ideal as if they continue to do it they can impare their swim bladder. It's called float, when they hold air and float around the tank, only to release the air bubble later.
I have also seen it when Fronts are fed with floating foods, which is a no no. They will gulp air and it could take a few days for it to pass through. You will notice that they float and or their backside with rise up slightly when the move and their head is slightly downward facing.