FS: ammonia alert (aquarium ammonia detector) stick on

Perfect companion for your fish, works in marine and fresh water tanks, now you can tell whether your fish are in danger
The color changing sensor( circle located in the middle) of Seachem's Ammonia Alert lets you know when free ammonia levels are dangerously high! Four levels of ammonia detection, safe, alert, alarm, and toxic, keeps you aware of your tank's current ammonia content.

Instructions:
Remove protective film. Place the unit visibly anywhere in the aquarium or filter. In the absence of free ammonia the unit will assume a yellow or faint yellow-green color. It may take up to a few days for a dry sensor to equilibrate with the water. The presence of free ammonia is detectable continuously with a response time of about 15 minutes. Response to decreasing ammonia is slower, requiring about four hours to go from "toxic" to "safe" upon removal of ammonia.

Specifications:
Remove algae growth from the sensor with a clean, soft material. Do not use bleach, soap, detergents or hard objects to clean the sensor. Avoid touching the sensor with fingers, since skin oils can damage it. Dye medications may discolor the sensor.