The concentration of dissolved Oxygen in water for growth of fish should be more than $\underset{¯}{\mathrm{X}} \mathrm{ppm}$ and Biochemical Oxygen Demand in clean water should be less than $\underset{¯}{\mathrm{Y}} \mathrm{ppm}$. $\mathrm{X}$ and $\mathrm{Y}$ in ppm are, respectively.

The concentration of dissolved oxygen in water is very important for aquatic life. If the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets inhibited. The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand (BOD). The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have BOD value of less than 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more.