The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is 4 ppm.
Dissolved oxygen (DO) is the amount of oxygen that is dissolved in water. It is essential for aquatic life, as it is used in respiration. The amount of DO in water can be affected by a number of factors, including temperature, salinity, and pollution.
The minimum DO concentration required for aquatic life varies depending on the type of organism. However, most fish and other aquatic animals require a DO concentration of at least 4 ppm. If the DO concentration drops below this level, it can lead to stress, illness, and even death.
There are a number of ways to improve the DO concentration in water. One way is to aerate the water, which can be done by adding air bubbles or by using a pump. Another way is to reduce pollution, which can be done by reducing the amount of sewage and other pollutants that are discharged into waterways.
It is important to monitor the DO concentration in water, as it can fluctuate significantly over time. If the DO concentration drops below the minimum level, it is important to take steps to improve the DO concentration, such as aerating the water or reducing pollution.