Nutrafin Phosphate 0.0 to 5.0 Mg/L for Fresh and Saltwater, 75 -Tests Suitable for fresh and saltwater aquariums to measure phosphate levels (0.0-5.0 Mg/L) Phosphate levels should generally never exceed 1 Mg/L Allows you to easily test phosphate levels Helps in the prevention of algae growth Easy to follow directions; Contains 75 tests