The alert combo combines the ph alert amp the ammonia alert into one packr ph alertr a unique colour device designed to be placed in the aquarium or filter and monitor ph continuouslyr a sensor changes colour reversibly to alert you to shifts in ph levels between 58 and 82r no tests no strips just constant readings freshwater onlyr lasts 3 to 6 months 4 times longer than competing products also half the sizer ammonia alert r an innovative colour device for continuously detecting a