Simple-to-use, professional-grade tester measures nitrate levels in your aquarium. Contains a lab-quality light emitting diode encased in a high-impact plastic housing. Includes two 10 ml cuvets and a 9-volt battery. Exclusive positive-locking system prevents user-error, while automatic shutoff feature conserves battery life. Uses light refraction to measure water turbidity from nitrate - which is formed during the decomposition of organic wastes. Measures between 0 to 30.0 mg/L. For Freshwater use only. Nitrate Reagent are precisely measured, single-use packets for use with 10 ml cuvets. Contains 100 packets. 2 year manufacturer's warranty.