Measures nitrate, nitrite, pH, GH, KH, and chlorine Results in 15 to 60 seconds Available in two sizes: 25 and 200 tests Frequently testing your water quality is one of the keys to successful fishkeeping. We developed the Aquarium Co-Op Multi-Test Strips to be fast, comprehensive, and accurate — which makes testing your aquarium water easier than ever. Measure nitrate, nitrite, hardness (GH), buffer (KH), pH, and chlorine levels in just 60 seconds. This test helps you understand your readings with helpful information and suggestions on the laminated color chart we've included. We created these to make your life easier and save you money when it comes to testing your water. 1. Holding the end of the test strip, dip into the aquarium so that all test pads are entirely submerged, and gently swirl the test strip for 3 seconds. 2. Remove the test strip from the aquarium without shaking the test strip. Keep the test strip horizontal as the colors develop. 3. After 15 seconds, compare the Hardness (GH), Buffer, KH, pH, and Chlorine results to the color chart.  4. After 60 seconds, compare the Nitrate and Nitrite results to the color chart. Notes:– Each bottle contains 25 or 200 test strips.– The test strips must stay dry for optimal accuracy. Do not leave the bottle cap off or humidity can affect the results. Keep inside of bottle dry and do not accidentally get the strips wet. Thoroughly dry your hands before grabbing a new test strip.– Store at room temperature.– Test strips expire 2 years after production.