The health of fish depends on the amount of oxygen dissolved in the water. A dissolved oxygen (DO) concentration between 6 parts per million and 8 parts per million is best for fish health. A DO concentration greater than 1 part per million is necessary for fish survival.
Fish health is also affected by water temperature and concentrations of dissolved
ammonia, hydrogen sulfide, chloride compounds, and nitrate compounds. Most freshwater fish thrive in water with a pH between 6.5 and 8.5.
A student’s fish tank contains fish, green plants, and 3800 grams of fish-tank water with 2.7 × 10–2 gram of dissolved oxygen. Phenolphthalein tests colorless and bromthymol blue tests blue in samples of the fish-tank water
When the fish-tank water has a pH of 8.0, the hydronium ion concentration is
1.0 × 10–8 mole per liter. What is the hydronium ion concentration when the water has
a pH of 7.0?