A small pond with a volume of 3500 m^3 has a pH of 4.2 and no fish. The owner wants to grow perch and needs the pH around 7.0. If the daily water flow into and out of the pond averages 30 m^3 per day with a pH similar to that of the pond, what is the minimum amount of limestone (CaCO3) needed to bring the pH to 7.0 and keep it there for 5 years? Why would you recommend using more than this in the pond? Hint: 1m^3=1000L