What is the Nitrogen Cycle?
The magic that makes it possible to keep aquarium fish alive and well in an aquarium.
The nitrogen cycle is a chain reaction in nature resulting in the birth of various types of nitrifying bacteria's, 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), nitrites (NO2) and nitrates (NO3).
What does this mean? The above explanation is the process that keeps your fish alive, the exact same process which occurs in our oceans, lakes and streams. Without this process your fish would be dead within days
To put the above explanation into terms you would understand it would go something like this. Your fish go to the bathroom, their waste turns into ammonia which is deadly and will kill your fish given the chance. That same waste, with the help of the above process, is then converted into a beneficial bacteria that needs ammonia to live. Therefore, each time your fish go to the bathroom this bacteria gladly consumes the ammonia thus leaving your aquarium toxin free.
Is this all there is to it? No, nothing is that easy, for every consumption there is an emission, in this circumstance the good bacteria converts into yet another deadly toxin called Nitrate. The only way to remove nitrate from your aquarium is by replacing your aquarium water, a water change. It's important to note that Nitrate is the least deadly and takes time to build up to a lethal dose.
Take a look at the chart below for a time table and the processing levels. The example below is not exact, but merely showing you what to expect.