API 5-IN-1 TEST STRIPS are the quick and easy way to test the 5 most important aquarium water parameters pH, KH, GH, nitrate, and nitrite in one easy step. Simply dip one test strip directly into the aquarium, and compare the colors on the strip to the color card provided to help prevent invisible water problems that can be harmful to fish. Each kit includes detailed information on how to interpret the test results and correct unsafe water conditions.