To know how toxic ammonia is to your fish, you must know the ammonia level, the pH level and the temperature. A total ammonia level of 10 ppm may not be harmful to trout at a pH of 6.0, but it would be deadly if the pH were 7.0. The test kits measure total ammonia. Total ammonia consists of both nontoxic NH4+ (ionized) and toxic NH3 (un-ionized) forms. The proportion of one to the other is variable.
The toxic form increases in proportion as the pH and/or temperature increases. Ammonia builds up in the water primarily by the metabolism of protein (nitrogen). About 10% of the protein fed to fish will show up as ammonia in the water. Testing takes 5 minutes. LM4795 range: 1 to 8 ppm. LM3351-01 range: 0.2 to 3 ppm.
Note: Water containing Ammo Lock and other ammonia-removing chemicals should be tested using an ammonia kit (LM3304) that uses the salicylate method (0 to 2.0 ppm).