Seachem One Year Combo AlertSeachem 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 readings No strips, no tests, just constant readings Easy monitoring just hang in your tank Ammonia Alert: The sensor automatically detects free ammonia at levels less than 0. 05 mg L (ppm)