Nutrafin Ammonia 0.0 to 7.3 Mg/L for Freshwater, 70 -Tests Suitable for freshwater aquariums to determine ammonia toxicity level (0.0-7.3 Mg/L) Best used with pH test kit to determine ammonia toxicity level (0.0-7.3 Mg/L) Helps you keep your fish free of toxics Weekly testing of ammonia levels will indicate if the biological filter activity is working efficiently Easy to follow directions; Contains 70 Tests