In an established tank, the reading of this test must show an undetectable level at all times. A detectable presence of total ammonia requires immediate action.
Ammonia is highly toxic in freshwater tanks, but even more toxic in reef and saltwater environments.
This is due to a higher pH level that causes the presence of ammonia gas, which in turn is far more toxic and easily water soluble. Even low concentrations of ammonia-N severely stress fish, making them vulnerable to diseases therefore shorting their life span. Lethal ammonia concentrations at a pH of 6.5 are 0.73 ppm, while at pH 8.5 only 0.17 ppm are considered lethal to inhabitants.