Goldfish floating head, sucking mouth. Why is there no lack of oxygen in the water?

Goldfish are floating, how do you know that there is no lack of oxygen? If the oxygen pump is always on and the water keeps bubbling, it may be that there is something wrong with the water quality. If there are no bubbles or few bubbles in the water, there is something wrong with the pump or insufficient oxygen supply. The specific situation is not clear, it is not easy to analyze, and it is for reference only.