pH Alert is a unique color device designed to be placed in the aquarium or filter and monitor pH continuously. A sensor changes color reversibly to alert you shifts to in pH levels between 5.8 and 8.2. No tests, no strips, just constant readings. Freshwater Only. pH Alert lasts up to 4 times as long as competing products. pH Alert is also almost half the size of competing products. It’s small, clear, and unobtrusive, so it won’t detract from the view of your aquarium. Simply place pH Alert visibly anywhere in the aquarium or filter. Its that easy. No chemicals or test procedures are required. When first put in service, response time will be about 30 minutes. Thereafter, pH shifts will register within ten minutes.