Seachem One Year Combo Alert uses Seachem water sensor technology to continuously monitor ammonia and freshwater pH in your aquarium for an entire year, no tests or strips required. All you have to do is hang it in your tank Continuous freshwater pH and ammonia readingsNo strips, no tests, just constant readingsEasy monitoring - just hang in your tankAmmonia Alert: The sensor automatically detects free ammonia at levels less than 0. 05 mg/L (ppm) and alerts you to the presence of the primary killer of fish before it reaches hazardous levels and causes signs of stress. In the absence of free ammonia the sensor will assume a yellow color, and will move to green and blue as more ammonia is detected. Ammonia is detected continuously with a response time of just 15 minutes, allowing you to respond immediately and avoid further increases. Ammonia Alert lasts over 9 times as long as competing products, and is only about half the size. pH Alert: pH is constantly monitored, with a sensor that alerts you to shifts in pH levels between 5. 4 and 8. 0 (freshwater only). It lasts up to 4 times as long as competing products and is small, clear, and unobtrusive when in the tank.