This simulation tests the effects of several factors on dissolved oxygen in a closed aquatic environment. You can select the number of fish and plants, the light intensity, the light color, and temperature. The simulation measures changes to dissolved oxygen levels (mg/L) over 60 minutes. This simulation can be used to study photosynthesis, cellular respiration, and ecosystem productivity. To test the fish alone, set the plant number to 0. To test only plants, set the fish to 0. To measure plant cellular respiration, set the light intensity to 0.