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 ppm. This product comes with one nitrite bottle, one capped glass test tube, one instruction manual and one color 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 almost 60 years API has developed premium solutions with proven and effective results for your family and ours. API offers a range of testing kits, water conditioners, and nutritionally superior food, because were dedicated to making a better underwater world. They work to provide a safe, hospitable environment for fish such as tropical community fish, cichlids, goldfish and more. At API, we understand the rewards and relaxation of fishkeeping because we have a passion for fish too.