Determine the nitrite level for optimal plant growth or the origin of algae in fresh and salt water. Comparative laboratory system to compensate for clean water coloring: fill test tubes with water to be tested, add reagents to a test tube, place test tubes in the holder block, read the values on the color chart. Use: new fresh water tank: once a week. New seawater tank: once a week. And in case of green algae problems. Included in delivery: 1 Nitrate Test for approx. 40 measurements, 2 reagents, 2 glass test tubes with screw cap, syringe, measuring spoon, comparator and colour chart. Reagent refills available separately.