This is a revised editorial from one of my previous articles. In this guide, I would like to emphasize why a nitrogen cycle is vital for aquarium care. Fish CANNOT live in an aquarium without nitrogen. It’s the simple. Adding fish into a tank directly after pouring water in does not work. This will stress out the fish for one, and the water is not properly cycled which would therefore kill most fish within the matter of a day. In regards to this, I will be explaining why the nitrogen cycle is important for life and how to start it in your aquarium.


Nitrogen as a Key Element

Nitrogen is one of the key elements on the periodic table, and is commonly found in nature. It is considered a non-metal and is abundant in every type of ecological system worldwide. And rightly so, because the Earth is made up of about 78% nitrogen. It helps all living things grow, reproduce, and survive. Nitrogen found throughout nature, both on land and sea, and is the key to survival for every living organism. Nitrogen can combine with many elements to create different compounds such as nitrites and nitrates (talked about further down), which are key components to all bodies of water. The diagram below represents the fundamentals of the nitrogen cycle and how it works in our everyday lives:

How to Start the Nitrogen Cycle

Starting a nitrogen cycle is a little different in an aquarium setting than nature. To begin, the nitrogen cycle is a process that requires three key elements: Ammonia (NH3), Nitrates (NO3), Nitrites (NO2). There are several ways to introduce this into your aquarium when starting up. I will list them below in bullet point form for ease of reading:

  • Live rock and sand – When buying live rock and sand, both will already have live bacteria in them which is very beneficial, and almost a must when starting up saltwater aquariums. This will typically start your nitrogen cycle faster, and let the cycling finish at a steady rate.
  • Quick start chemicals – This is not my preferred way of starting up the nitrogen cycle since you are adding chemicals to your water which isn’t natural, but it does add a good source of bacteria and ammonia into the water to help start the cycle quickly.
  • Table shrimp – This method is a little gross but has been proven to be effective. Essentially you throw in raw, uncooked shrimp that you can purchase at any local grocery store into your tank. This adds natural ammonia to the water. You will typically let the shrimp sit in the water for a day or two before taking it out.
  • Ghost feeding – This is how I normally start up freshwater tanks, but it can be done with saltwater as well in addition to live rock and sand. You will put a very small pinch of your flaked or frozen fish food into the aquarium and let it cycle through the filter pad. This will start filtering ammonia into the tank to help out with the nitrogen cycle.
  • Live fish – This is not a preferred method of starting up the cycle, but it is a method nonetheless. In this method, you will add a cheap saltwater fish to your tank such as a damsel or chromis since they are hardy fish, and let them add ammonia and bacteria to the water naturally. *The fish may die in the process!*


How Long Will the Cycle Take?

The nitrogen cycle will typically take anywhere from 2 to 6 weeks for saltwater aquariums. Sometimes it can differ if you have ideal parameters, along with natural carriers of bacteria to start the nitrogen cycle. You should never try rushing a saltwater tank when cycling, as difficult as it may be sitting there with an empty tank. Many people have tried and they will all tell you that it is worth waiting for the cycle to be 100% complete. This will prevent you from coming across any detrimental effects later on with your aquarium. It is also important to check your water parameters every few days in order to watch gradual changes in your ammonia, nitrates, and nitrites. The parameters should start off being moderately high, and slowly fall back down on your testing throughout the week. Once all the numbers go down to zero then your tank is finished cycling. Your readings should look similar to this image below: