Keep your fish healthy and thriving by testing your aquarium water’s NO2 levels regularly with this easy-to-use API NITRITE TEST KIT for freshwater and saltwater aquariums. Testing water parameters weekly helps prevent invisible water problems that can be harmful to fish.Nitrite is produced in the aquarium by fish waste and uneaten fish food. Low levels of nitrite inhibit respiration and suppress the immune system; high levels cause suffocation. The API NITRITE TEST KIT tests for harmful nitrite levels from 0 to 5 mg/L. This product comes with one nitrite bottle, one capped glass test tube, one instruction manual and one colour card. API NITRITE TEST KIT can be used in freshwater and saltwater aquariums. With API Aquarium products, its easy to keep a beautiful saltwater, freshwater or reef aquarium. For over 50 years, API has been creating innovative, research-driven solutions that make it easier to care for your fish and aquarium. API Aquarium Treatment Supplies are designed to work in conjunction with each other to provide best results to control algae, promote healthy bacterial growth and help control and cure fish diseases and conditions such as ich and fin rot. They work to provide a safe, hospitable environment for fish such as tropical community fish, cichlids, goldfish and more. With API, you can spend more time admiring your fish, and less time scrubbing your tank. Make sure to use all products as directed in order to ensure the best results.