The nitrogen cycle of an aquarium is a chain reaction in nature resulting in the birth of various types of nitrifying bacteria, each with their own job to do. Each new bacteria born consumes the previous one, and in turn gives birth to the next bacteria.
The three components involved to make this happen are ammonia (NH³ or NH³+4), nitrite (NO²), and nitrate (NO³).Ammonia being the most toxic then nitrite.Although not as toxic as ammonia,it still can be deadly to life in your system.Nitrate is the final by-product of nitrite consuming bacteria.Its the least deadliest of the three and in small amounts is considered harmless in a way.