What does it mean when all the fish emerge from the bottom of the river?

First of all, fish always surface with the following possibilities:

1, some fish are close to the water surface and rarely go to the bottom, such as the tooth butterfly fish.

2. When the dissolved oxygen content in water is less than 3mg/L, most fish will float their heads due to lack of oxygen, so it is necessary to increase oxygen and change water in time.

3, chlorine poisoning, ammonia poisoning, nitrite poisoning, fish will also float due to lack of oxygen, and it is necessary to increase oxygen and change water in time.

4, infectious gill injury, weakened breathing, fish will always surface, need the right medicine.

Second, although fish is the lowest vertebrate, it already has quite complete organ systems such as bones, muscles, digestion, circulation, respiration, excretion, reproduction and nerve sensation, and can carry out extremely diverse life activities. Its morphological structure is not only related to systematic development, but also reflects its adaptability to water environment.