Goldfish spit bubbles because of lack of oxygen in water and insufficient dissolved oxygen in water environment. When there is no oxygen in the water, the goldfish will float to the surface and its mouth will open and close. If you listen carefully, you will hear the sound of "beep, beep" from the goldfish mouth. They can't get oxygen from the water, so they can only spit bubbles on the water to breathe oxygen.

There are many reasons for the lack of dissolved oxygen in water. For example:

There are many fish in the water, but the space of the whole fish tank is small and there is little water, which easily leads to hypoxia in the water environment and makes goldfish spit bubbles.

There are too many food residues in the water environment, and the excrement of fish accumulates, which leads to the corruption of the water environment, the water quality can not be better purified for a long time, and the oxygen in the water will gradually decrease. When oxygen is insufficient, goldfish will spit bubbles.

PS: To avoid goldfish spitting bubbles, it is necessary to ensure that the dissolved oxygen in the water environment is sufficient. In addition, we must ensure that the water quality environment is healthy and stable, so that goldfish can live a more stable and healthy life. Remember, "raising fish first raises water" is the most fundamental and important principle for raising goldfish.