SeaChem Ammonia Alert is an innovative colour device for continuously detecting and monitoring toxic free ammonia. A sensor changes reversibly from yellow to green to blue, relative to the ammonia concentration. 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. Marine or freshwater use. In the absence of free ammonia the unit will assume a yellow or faint yellow-green colour. 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. No sampling of water, chemicals, or test procedures are required. The presence of the free ammonia is detectable continuously with a response time of about 15 minutes. Response to decreasing ammonia is slower, requiring about 4 hours to go from TOXIC to SAFE on removal of ammonia. Why Its Different Ammonia Alert lasts over 9 times as long as competing products (over a year compared to 4-6 weeks). Ammonia 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. Care No care is required beyond removing algae with a clean, soft material. Avoid touching the sensor with fingers, since skin oils can damage it. Do not use bleach, soap, detergents or hard objects to clean the sensor. Some dye medications may discolour the sensor. Sensitivity improves with age, provided the unit is not allowed to dry out, however, drying does not permanently impair the unit. For maximum sensitivity, the unit should be read under natural daylight or daylight simulating light. The response of the unit may be checked by holding it briefly over the mouth of an ammonia bottle: colour should develop rapidly.