Regular testing of pH, Nitrite, Nitrate, Carbonate Hardness (KH), and General Hardness (GH) is an essential part of pond ownership and maintenance. In order for fish to thrive, pond water must mimic the conditions of their natural habitat. Improper chemisty levels can cause fish stress which can lead to illness or even death. PondCare 5-in-1 Test Strips use highly accurate color charts for precise test results. Chart colors are distinctive, making them easy to read, and the snap-tight tube offers superior moisture protection to ensure uncompromised results and a lengthy shelf-life. Use as directed.