Seachem Alert Combo pH & Ammonia Reading Pack for Freshwater Aquariums combines two great products into one convenient package for continuous monitoring of both ammonia and pH in freshwater. Ammonia Alert monitors free ammonia levels in marine and freshwater aquariums, and lasts up to 1 year. And pH alert monitors pH in freshwater aquariums, lasting up to 6 months. Both of these monitors are small and unobtrusive. And they’re easy to set up — simply place the alerts in the aquarium or filter where you can see them. No chemicals. No tests. Just simple, effective, effortless monitoring you can count on.

• An innovative color device for continuously detecting and monitoring toxic free ammonia. A sensor changes reversibly from yellow to green to blue, relative to the ammonia concentration. 
• Combo includes one pH Alert and one Ammonia Alert and provides continuous monitoring for ammonia and pH.
• No test kits, chemicals, or procedures are needed. The device detects less than 0.05 mg/L (ppm) free ammonia and alerts you to the #1 killer before any sign of stress. It lasts over a year. Marine or freshwater use.
• In the absence of free ammonia the unit will assume a yellow or faint yellow-green color. It is normal for the dry sensor to have a greenish hue. 
• It may take up to a few days for a dry sensor to equilibrate with the water.