An alkaline ingredient used in some permanent hair color. Ammonia is an ingredient that results in a chemical action that decolorizes the hair. A colorless, pungent gas, NH3, extensively used to manufacture fertilisers and a wide variety of nitrogen-containing organic and inorganic chemicals. This is the first step in the nitrogen cycle. Ammonia is generated by fish urine and by the decay of dead fish and plant material. It is perhaps the deadliest agent to tropical fish. Care must be made to ensure that the ammonia levels stay at zero.