How Much Dissolved Oxygen Do Fish Need In Ppm?

How Much Dissolved Oxygen Do Fish Need In Ppm? Fish growth and activity usually require 5-6 ppm of dissolved oxygen. Dissolved oxygen levels below 3 ppm are stressful to most aquatic organisms. Levels below 2 ppm will not support fish at all. What ppm do fish need? Ideally, freshwater aquariums have a GH between 4-8