Measuring Light Intensity By Dana Riddle If I were to ask reef aquarium hobbyists these questions, their answers would likely be as follows: Q: What is the Specific Gravity of the water in your tank? A: 1.025 Q: What is your calcium concentration? A: 400 milligrams per liter (or parts per million) Q: What is … Continue reading Lighting the Reef Aquarium Part 2-Measuring Light Intensity