Red Sea Fish Pharm ARE21406 Reagent Calcium Pro Refill Kit for Aquarium, 75 Tests Calcium pro test kit is an advanced calcium titration test Test refill replenishes calcium pro test kit with sufficient reagent to conduct another 75 tests Measuring the level of calcium in reef aquarium to an exceptionally high accuracy of 5 ppm Calcium, an essential component in the building of coral skeletons, is constantly depleted from the aquarium and needs Conventional titration testing involves a cumbersome process of adding and mixing a titrant with sample water containing reagents